,illu/ration3 ,,plate ,i4 ,maps ,i4-,,iv4 ,,half-,,h\rs ,,) ,,! ,,telescope2 ,,be+ ,a ,,popul> ,,guide ,,to ,,! ,,use ,,( ,,! ,,telescope ,,z ,a ,,means ,,( ,,amusem5t ,,& ,,in/ruction4 ,,by ,,ri*>d ,a4 ,,proctor1 ,b4,a41 ,f4,r4,a4,s41 ,,au?or ,,( ,,saturn ,,& ,,its ,,sy/em1 ,,etc4 ,,) ,,illu/rations ,,on ,,/one ,,& ,,wood4 99 99 99 99 99 ,an undev\t a/ronom] is mad3 ,true1 all ?+s speak a ,god2 b1 9 ! small ,m5 trace out ,him3 9 great ,he seizes man4 ,,"y4 99 99 99 99 99 ,,new ,,york3 ,g4,p4 ,,putnam',s ,,sons4 #ahgc4 ,,london3 ,,pr9t$ ,,by ,,william ,,cl[es ,,& ,,sons1 ,,/am=d ,,/reet ,,& ,,*>+ ,,cross4 ,,preface4 ,! object :i* ! ,au?or & ,publi%] ( ?is little "w h propos$ to !mselves1 has be5 ! production1 at a mod]ate price1 ( a useful & reliable guide to ! amateur telescopi/4 ,among ! cele/ial ph5om5a describ$ or figur$ 9 ?is treatise1 by f> ! l>g] numb] may be pr(itably exam9$ ) small telescopes1 & !re are none :i* are beyond ! range ( a good #c-;in* a*romatic4 ,! "w also treats ( ! con/ruction ( telescopes1 ! nature & use ( />-maps1 & o!r subjects connect$ ) ! requirem5ts ( amateur obs]v]s4 ,r4,a4,p4 ,janu>y1 #ahfh4 ,,cont5ts4 ,,*apt] ,i4 ,,page ,a ,,half-,,h\r ,,on ,,! ,,/ructure ,,( ,,! ,,telescope #a ,,*apt] ,,ii4 ,a ,,half-,,h\r ,,) ,,orion1 ,,lepus1 ,,taurus1 ,,etc4 #cc ,,*apt] ,,iii4 ,a ,,half-,,h\r ,,) ,,lyra1 ,,h]cules1 ,,corvus1 ,,crat]1 ,,etc4 #dg ,,*apt] ,,iv4 ,a ,,half-,,h\r ,,) ,,bootes1 ,,scorpio1 ,,ophiu*us1 ,,etc4 #ef ,,*apt] ,v4 ,a ,,half-,,h\r ,,) ,,&rom$a1 ,,cygnus1 ,,etc4 #ff ,,*apt] ,,vi4 ,,half-,,h\rs ,,) ,,! ,,planets #gd ,,*apt] ,,vii4 ,,half-,,h\rs ,,) ,,! ,,sun ,,& ,,moon #ic ,,description ,,( ,,plates4 ,,plate ,i4--,frontispiece4 ,?is plate pres5ts ! aspect ( ! heav5s at ! f\r seasons1 dealt ) 9 ,*apt]s ,,ii41 ,,iii41 ,,iv41 & ,v4 ,9 ea* map ( ?is plate ! c5tral po9t repres5ts ! po9t v]tically ov] ! obs]v]'s head1 & ! circumf]5ce repres5ts 8 horizon4 ,! plan ( ea* map is su* t ! direction ( a /> or con/ellation1 z respects ! compass-po9ts1 & its elevation1 also1 above ! horizon1 at ! giv5 season1 c be at once det]m9$4 ,two illu/rations ( ! use ( ! maps w s]ve to expla9 _! nature bett] ?an any detail$ description4 ,suppose fir/1 t--at "o ( ! h\rs nam$ "u ,map ,i4--! obs]v] wi%es to f9d ,ca/or & ,pollux3--,turn+ to ,map ,i4 he sees t ^! />s lie 9 ! l[] left-h& quadrant1 & v ne>ly t[>ds ! po9t m>k$ ,s4,e42 t is1 !y are to be look$ = on ! sky t[>ds ! s\?-ea/4 ,also1 x is se5 t ! two />s lie ab\t "o-f\r? ( ! way f ! c5tre t[>ds ! circumf]5ce4 ,h5ce1 on ! sky1 ! />s w be f\nd ab\t "o-f\r? ( ! way f ! z5i? t[>ds ! horizon3 ,ca/or w be se5 imm$iately above ,pollux4 ,next1 suppose t at "o ( ! h\rs nam$ ! obs]v] wi%es to le>n :at />s are visible t[>ds ! we/ & nor?-we/3--,turn+ ! map until ! portion ( ! circumf]5ce m>k$ ,w 444 ,n4,w4 is l[]mo/1 he sees t 9 ! direction nam$ ! squ>e ( ,pegasus lies n v high above ! horizon1 "o diagonal ( ! squ>e be+ v]tical1 ! o!r ne>ly horizontal4 ,above ! squ>e is ,&rom$a1 to ! "r ( :i* lies ,cassiopeia1 ! />s beta & epsilon ( ?is con/ellation ly+ directly t[>ds ! nor?-we/1 :ile ! /> alpha lies almo/ exactly midway betwe5 ! z5i? & ! horizon4 ,above ,&rom$a1 a little t[>ds ! left1 lies ,p]seus1 ,algol be+ almo/ exactly t[>ds ! we/ & "o-?ird ( ! way f ! z5i? t[>ds ! horizon 7because "o-?ird ( ! way f ! c5tre t[>ds ! circumf]5ce ( ! map74 ,almo/ exactly 9 ! z5i? is ! /> delta ,aurig4 ,! f\r maps are m9iatures ( ,maps ,i41 ,,iv41 ,,vii41 & ,x4 ( my ',con/ellation ,seasons1' f\r?-magnitude />s1 h[ev]1 be+ omitt$4 ,,plates ,,ii41 ,,iii41 ,,iv41 & ,v41 illu/rat+ ,*apt]s ,,ii41 ,,iii41 ,,iv41 & ,v4 ,plates ,,ii4 & ,,iv4 conta9 f\r />-maps4 ,!y n only s]ve to indicate ! configuration ( c]ta9 important />-gr\ps1 b !y illu/rate ! con/ruction ( maps1 su* z ! obs]v] %\ld make = himself :5 he wi%es to obta9 an accurate k ( p>ticul> regions ( ! sky4 ,!y are all made to "o scale1 & on ! conical projection--! simple/ & be/ ( all projections = maps ( ?is sort4 ,! way 9 :i* ! m]idians & p>allels = ?is projection are laid d[n is describ$ 9 my ',h&book ( ! ,/>s4' ,) a little practice a few m9utes w suffice = sweep+ out ! equidi/ant circul> arcs :i* m>k ! p>allels & rul+ 9 ! /raight m]idians4 ,! dott$ l9e across ?ree ( ! maps repres5ts a portion ( ! horizontal circle midway betwe5 ! z5i? & ! horizon at ! h\r at :i* ! map is suppos$ to be us$4 ,at o!r h\rs1 ( c\rse1 ?is l9e w\ld be diff]5tly situat$4 ,plates ,,iii4 & ,v4 repres5t fifty-two ( ! objects m5tion$ 9 ! above-nam$ *apt]s4 ,z ref]5ce is made to ^! figures 9 ! text1 little comm5t is "h requir$4 ,x is to be rem>k$1 h[ev]1 t ! circles1 & especially ! small circles1 d n repres5t ! :ole ( ! telescope's field ( view1 only a small portion ( x4 ,! object ( ^! figures is to enable ! obs]v] to "k :at to expect :5 he turns 8 telescope t[>ds a difficult d\ble />4 ,_m ( ! objects depict$ are v easy d\bles3 ^! are giv5 z objects ( ref]5ce4 ,! obs]v] hav+ se5 ! correspond5ce betwe5 an easy d\ble & its picture1 z respects ! relation betwe5 ! l9e jo9+ ! compon5ts & ! app>5t pa? ( ! d\ble across ! telescope's field ( view1 w "k h[ to int]pret ! picture ( a difficult d\ble 9 ?is respect4 ,& z all ! small figures are drawn to "o scale1 he w also "k h[ f> ap>t he may expect to f9d ! compon5ts ( a difficult d\ble4 ,?us he w h an exact conception ( ! sort ( duplicity he is to look =1 & ?is is--cr$e exp]to--a great /ep t[>ds ! detection ( ! />'s duplicity4 ,,plates ,,vi4 & ,,vii41 illu/rat+ ,*apt]s ,,vi4 & ,,vii4 ,! views ( ,m]cury1 ,v5us1 & ,m>s 9 ^! plates 7except ! small] view ( ,jupit] 9 ,plate ,,vii47 are suppos$ to be se5 ) ! same p[]4 ,! obs]v] mu/ n expect to see ! details pres5t$ 9 ! views ( ,m>s ) any?+ l ! di/9ctness ,i h "h giv5 to !m4 ,if he place ! plate at a di/ance ( six or sev5 y>ds he w see ! views m ne>ly z ,m>s is likely to appe> 9 a good ?ree-in* ap]ture4 ,! *>t ( ,m>s is a r$uction ( "o ,i h con/ruct$ f views by ,mr4 ,dawes4 ,i believe t ne>ly all ! features includ$ 9 ! *>t are p]man5t1 ?\gh n always visible4 ,i take ?is opportunity ( not+ t ! eighte5 or?ographic pictures ( ,m>s pres5t$ ) my %ill+ *>t are to be look$ on r z maps ?an z repres5t+ telescopic views4 ,!y illu/rate usefully ! v>y+ pres5tation ( ,m>s t[>ds ! e>?4 ,! obs]v] c obta9 o!r su* illu/rations = himself by fill+ 9 outl9es1 trac$ f ^? giv5 at ! foot ( ,plate ,,vi41 ) details f ! *>t4 ,x is to be not$ t ,m>s v>ies 9 pres5tation1 n only z respects ! great] or less op5+ out ( 8 equator t[>ds ! nor? or s\?1 b z respects ! app>5t slope ( 8 pol> axis to ! "r or left4 ,! f\r projections z %[n1 or inv]t$1 or se5 f ! back ( ! plate 7held up to ! light7 give pres5tations ( ,m>s t[>ds ! sun at twelve p]iods ( ! ,m>tial ye>1--viz41 at ! autumnal & v]nal equ9oxes1 at ! two sol/ices1 & at int]m$iate p]iods correspond+ to our t]re/rial mon?s4 ,9 fact1 by means ( ^! projections "o might readily =m a s]ies ( sun-views ( ,m>s resembl+ my ',sun-views ( ! ,e>?4' ,9 ! fir/ view ( ,jupit] x is to be rem>k$ t ! ?ree satellites outside ! disc are suppos$ to be mov+ 9 directions appreciably p>allel to ! belts on ! disc--! upp] satellites f "r to left1 ! l[] "o f left to "r4 ,9 g5]al ! satellites1 :5 s ne> to ! disc1 are n se5 9 a /raight l9e1 z ! ?ree %[n 9 ! figure happ5 to be4 ,( ! ?ree spots on ! disc1 ! fa9te/ is a satellite1 ! neighb\r+ d>k spot its %ad[1 ! o!r d>k spot ! %ad[ ( ! satellite close to ! planet's disc4 ,,half-,,h\rs ,,) ,,! ,,telescope4 ,,*apt] ,i4 ,a ,,half-,,h\r ,,on ,,! ,,/ructure ,,( ,,! ,,telescope4 ,!re are few in/rum5ts :i* yield m pleasure & in/ruction ?an ! ,telescope4 ,ev5 a small telescope--only an in* & a half or two in*es1 p]haps1 9 ap]ture--w s]ve to supply pr(itable amusem5t to ^? :o "k h[ to apply its p[]s4 ,i h (t5 se5 ) pleasure ! surprise ) :i* ! p]=mance ev5 ( an op]a-glass1 well /eadi$1 & direct$ t[>ds c]ta9 p>ts ( ! heav5s1 has be5 witness$ by ^? :o h suppos$ t no?+ b an exp5sive & colossal telescope c\ld af=d any views ( int]e/4 ,b a well-con/ruct$ a*romatic ( two or ?ree in*es 9 ap]ture w n m]ely supply amusem5t & in/ruction1--x may be made to d useful "w4 ,! /ud5t ( a/ronomy is (t5 det]r$ f telescopic obs]vation by ! ?\ght t 9 a field :]e9 s _m h lab\r$1 ) abilities & means p]haps f> surpass+ ^? he may possess1 he is little likely to reap results ( any utility4 ,he argues t1 s9ce ! planets1 />s1 & nebul h be5 scann$ by ,h]s*el & ,rosse1 ) _! gigantic mirrors1 & at ,pulkova & ,gre5wi* ) refractors ^: con/ruction has tax$ to ! utmo/ ! +5uity ( ! optician & me*anic1 x mu/ be utt]ly useless = an unpractis$ obs]v] to direct a telescope ( mod]ate p[] to ! exam9ation ( ^! objects4 ,n[1 pass+ ov] ! consid]ation t a small telescope may af=d its possessor mu* pleasure ( an intellectual & elevat$ "*1 ev5 if he is nev] able by its means to effect orig9al discov]ies1 two argum5ts may be urg$ 9 fav\r ( indep5d5t telescopic obs]vation4 ,9 ! fir/ place1 ! /ud5t :o wi%es to appreciate ! facts & !ories ( a/ronomy %\ld famili>ize himself ) ! nature ( t in/rum5t to :i* a/ronom]s h be5 mo/ l>gely indebt$4 ,9 ! second place1 "s ( ! mo/ important discov]ies 9 a/ronomy h be5 effect$ by means ( telescopes ( mod]ate p[] us$ skilfully & sy/ematically4 ,"o in/ance may suffice to %[ :at c be done 9 ?is way4 ,! well-kn[n telescopi/ ,golds*midt 7:o comm5c$ a/ronomical obs]vation at ! age ( =ty-eight1 9 #ahej7 add$ f\rte5 a/]oids to ! sol> sy/em1 n to speak ( important discov]ies ( nebul & v>iable />s1 by means ( a telescope only five feet 9 focal l5g?1 m\nt$ on a movable tripod /&4 ,! feel+ exp]i5c$ by ^? :o look ?r\gh a telescope = ! fir/ "t1--especially if x is direct$ ^u a planet or nebula--is commonly "o ( disappo9tm5t4 ,!y h be5 told t su* & su* p[]s w exhibit ,jupit]'s belts1 ,saturn's r+s1 & ! cont95t-outl9es on ,m>s2 yet1 ?\gh p]haps a high] p[] is appli$1 !y fail to detect ^! appe>ances1 & c h>dly believe t !y are p]fectly di/9ct to ! practis$ eye4 ,! expectations ( ! beg9n] are especially liable to disappo9tm5t 9 "o p>ticul>4 ,he =ms an e/imate ( ! view he is to obta9 ( a planet by multiply+ ! app>5t diamet] ( ! planet by ! magnify+ p[] ( 8 telescope1 & comp>+ ! result ) ! app>5t diamet] ( ! sun or moon4 ,let u suppose1 = in/ance1 t on ! day ( obs]vation ,jupit]'s app>5t diamet] is #de1 & t ! telescopic p[] appli$ is #dj1 !n 9 ! telescope ,jupit] %\ld appe> to h a diamet] ( #ahjj1 or half a degree1 :i* is ab\t ! same z ! moon's app>5t diamet]4 ,b :5 ! obs]v] looks ?r\gh ! telescope he obta9s a view--int]e/+1 inde$1 & in/ructive--b v diff]5t f :at ! above calculation w\ld lead him to expect4 ,he sees a disc app>5tly mu* small] ?an ! moon's1 & n ne>ly s well-def9$ 9 outl9e2 9 a l9e ) ! disc's c5tre !re appe> ?ree or f\r m9ute dots ( light1 ! satellites ( ! planet2 &1 p]haps1 if ! wea!r is fav\rable & ! obs]v] wat*ful1 he w be able to detect fa9t traces ( belts across ! planet's disc4 ,yet 9 su* a case ! telescope is n 9 fault4 ,! planet really appe>s ( ! e/imat$ size4 ,9 fact1 x is (t5 possible to prove ?is 9 a v simple mann]4 ,if ! obs]v] wait until ! planet & ! moon are pretty ne> toge!r1 he w f9d t x is possible to view ! planet ) "o eye ?r\gh ! telescope & ! moon ) ! unaid$ eye1 9 su* a mann] t ! two discs may co9cide1 & ?us _! relative app>5t dim5sions be at once recognis$4 ,nor %\ld ! indi/9ctness & incomplet5ess ( ! view be attribut$ to imp]fection ( ! telescope2 !y are p>tly due to ! nature ( ! obs]vation & ! l[ p[] employ$1 & p>tly to ! inexp]i5ce ( ! beg9n]4 ,x is to su* a beg9n] t ! foll[+ pages are specially address$1 ) ! hope ( af=d+ him aid & enc\ragem5t 9 ! use ( "o ( ! mo/ en*ant+ ( sci5tific in/rum5ts1--an in/rum5t t has creat$ = a/ronom]s a new s5se1 s to speak1 by :i*1 9 ! words ( ! anci5t poet3 ,subjec]e oculis di/antia sid]a no/ris1 !raque +5io supposu]e suo4 ,9 ! fir/ place1 x is necess>y t ! beg9n] %\ld rightly "k :at is ! nature ( ! in/rum5t he is to use4 ,& ?is is ! m necess>y because1 :ile x is p]fectly easy to obta9 su* k )\t any pr(\nd acqua9tance ) ! sci5ce ( optics1 yet 9 _m popul> works on ?is subject ! really important po9ts are omitt$1 & ev5 9 sci5tific works su* po9ts are too (t5 left to be ga!r$ f a =mula4 ,:5 ! obs]v] has le>nt :at x is t 8 in/rum5t is actually to d = him1 he w "k h[ to e/imate its p]=mance1 & h[ to v>y ! application ( its p[]s--:e!r illum9at+ or magnify+--accord+ to ! nature ( ! object to be obs]v$4 ,let u consid] :at x is t limits ! range ( natural vision appli$ to di/ant objects4 ,:at causes an object to become invisible z its di/ance increases8 ,two ?+s are necess>y t an object %\ld be visible4 ,x mu/ be l>ge en\gh to be appreciat$ by ! eye1 & x mu/ s5d light en\gh4 ,?us increase ( di/ance may r5d] an object invisible1 ei!r ?r\gh dim9ution ( its app>5t size1 or ?r\gh dim9ution 9 ! quantity ( light x s5ds to ! eye1 or ?r\gh bo? ^! causes comb9$4 ,a telescope1 !re=e1 or 7z its "n implies7 an in/rum5t to r5d] di/ant objects visible1 mu/ be bo? a magnify+ & an illum9at+ in/rum5t4 ,illu/ration3 ,fig4 #a4 ,let ,,ef1 fig4 #a1 be an object1 n ne> to ,,ab z 9 ! figure1 b s f> (f t ! b\nd+ l9es f ,a & ,b w\ld meet at ! po9t correspond+ to ! po9t ,p4 ,!n if a l>ge convex glass ,,ab 7call$ an object-glass7 be int]pos$ betwe5 ! object & ! eye1 all ^? rays :i*1 proce$+ f ,p1 fall on ,,ab1 w be caus$ to conv]ge ne>ly to a po9t p4 ,! same is true = e po9t ( ! object ,,emf1 & ?us a small image1 emf1 w be =m$4 ,?is image w n lie exactly on a flat surface1 b w be curv$ ab\t ! po9t midway betwe5 ,a & ,b z a c5tre4 ,n[ if ! l5s ,,ab is remov$1 & an eye is plac$ at m to view ! di/ant object ,,emf1 ^? rays only f ea* po9t ( ! object :i* fall on ! pupil ( ! eye 7^: diamet] is ab\t equal to mp suppose7 w s]ve to r5d] ! object visible4 ,on ! o!r h&1 e po9t ( ! image emf has receiv$ ! :ole ( ! light ga!r$ up by ! l>ge glass ,,ab4 ,if !n we c only make ?is light available1 x is cle> t we %all h acquir$ a l>ge increase ( light f ! di/ant object4 ,n[ x w be notic$ t ! light :i* has conv]g$ to p1 div]ges f p s t an eye1 plac$ t ?is div]g+ p5cil ( rays may fall ^u x1 w\ld be too small to receive ! :ole ( ! p5cil4 ,or1 if x did receive ! :ole ( ?is p5cil1 x cle>ly c\ld n receive ! :ole ( ! p5cils proce$+ f o!r p>ts ( ! image emf4 ,some?+ w\ld be ga9$1 ?\gh1 ev5 9 ?is case1 s9ce x is cle> t an eye ?us plac$ at a di/ance ( t5 in*es f emf 7:i* is ab\t ! av]age di/ance ( di/9ct vision7 w\ld n only receive mu* m light f ! image emf1 ?an x w\ld f ! object ,,emf1 b see ! image mu* l>g] ?an ! object4 ,x is 9 ?is way t a simple object-glass =ms a telescope1 a circum/ance we %all pres5tly h to notice m at l5g?4 ,b we want to ga9 ! full b5efit ( ! light :i* has be5 ga!r$ up = u by our object-glass4 ,we !re=e int]pose a small convex glass ab 7call$ an eye-glass7 betwe5 ! image & ! eye1 at su* a di/ance f ! image t ! div]g5t p5cil ( rays is conv]t$ into a p5cil ( p>allel or ne>ly p>allel rays4 ,call ?is an em]g5t p5cil4 ,!n all ! em]g5t p5cils n[ conv]ge to a po9t on ! axial l9e m,m 7produc$ beyond m71 & an eye suitably plac$ c take 9 all ( !m at once4 ,?us ! :ole1 or a l>ge "p1 ( ! image is se5 at once4 ,b ! image is se5 inv]t$ z %[n4 ,?is is ! ,telescope1 z x 0 fir/ discov]$1 & su* an arrangem5t w\ld n[ be call$ a simple a/ronomical ,telescope4 ,let u cle>ly und]/& :at ea* "p ( ! a/ronomical telescope does = u3-- ,! object-glass ,,ab gives u an illum9at$ image1 ! am\nt ( illum9ation dep5d+ on ! size ( ! object-glass4 ,! eye-glass enables u to exam9e ! image microscopically4 ,we may apply eye-glasses ( diff]5t focal l5g?4 ,x is cle> t ! %ort] ! focal l5g? ( ab1 ! ne>] mu/ ab be plac$ to ! image1 & ! small] w ! em]g5t p5cils be1 b ! great] ! magnify+ p[] ( ! eye-glass4 ,if ! em]g5t p5cils are sev]ally l>g] ?an ! pupil ( ! eye1 light is wa/$ at ! exp5se ( magnify+ p[]4 ,!re=e ! eye-glass %\ld nev] be ( great] focal l5g? ?an t :i* makes ! em]g5t p5cils ab\t equal 9 diamet] to ! pupil ( ! eye4 ,on ! o!r h&1 ! eye-glass mu/ n be ( su* small focal l5g? t ! image appe>s indi/9ct & contort$1 or dull = want ( light4 ,illu/ration3 ,fig4 #b4 ,let u comp>e ) ! arrangem5t exhibit$ 9 fig4 #a t adopt$ by ,galileo4 ,surprise is sometimes express$ t ?is in/rum5t1 :i* 9 ! h&s ( ! great ,flor5t9e a/ronom] effect$ s mu*1 %\ld n[ be kn[n z ! non-a/ronomical ,telescope4 ,i ?9k ?is w be readily und]/ood :5 we comp>e ! two arrangem5ts4 ,9 ! ,galilean ,telescope a small concave eye-glass1 ab 7fig4 #b71 is plac$ betwe5 ! object-glass & ! image4 ,9 fact1 no image is all[$ to be =m$ 9 ?is arrangem5t1 b ! conv]g5t p5cils are int]cept$ by ! concave eye-glass1 & conv]t$ into p>allel em]g5t p5cils4 ,n[ 9 fig4 #b ! concave eye-glass is s plac$ z to receive only a "p ( ! conv]g5t p5cil ,a p ,b1 & ?is is ! arrangem5t usually adopt$4 ,by us+ a concave glass ( %ort] focus1 :i* w\ld !re=e be plac$ ne>] to m p1 ! :ole ( ! conv]g5t p5cil might be receiv$ 9 ?is z 9 ! =m] case4 ,b !n ! axis ( ! em]g5t p5cil1 in/ead ( return+ 7z we see x 9 fig4 #a7 t[>ds ! axis ( ! telescope1 w\ld dep>t z mu* f t axis4 ,?us !re w\ld be no po9t on ! axis at :i* ! eye c\ld be s plac$ z to receive em]g5t p5cils %[+ any consid]able "p ( ! object4 ,! diff]5ce may be comp>$ to t betwe5 look+ ?r\gh ! small end ( a cone-%ap$ roll ( pap] & look+ ?r\gh ! l>ge end2 9 ! =m] case ! eye sees at once all t is to be se5 ?r\gh ! roll 7suppos$ fix$ 9 position71 9 ! latt] ! eye may be mov$ ab\t s z to comm& ! same range ( view1 b at any in/ant sees ov] a mu* small] range4 ,to return to ! arrangem5t actually employ$1 :i* is illu/rat$ by ! common op]a-glass4 ,we see t ! full illum9at+ p[] ( ! telescope is n br\ght into play4 ,b ?is is n ! only objection to ! ,galilean ,telescope4 ,x is obvi\s t if ! "p ,c ,d ( ! object-glass 7 cov]$1 ! po9t ,p w\ld n be visible1 :]eas1 9 ! a/ronomical arrangem5t no o!r effect is produc$ on ! visibility ( an object1 by cov]+ "p ( ! object-glass1 ?an a small loss ( illum9ation4 ,9 o!r words1 ! dim5sions ( ! field ( view ( a ,galilean ,telescope dep5d on ! size ( ! object-glass1 :]eas 9 ! a/ronomical ,telescope ! field ( view is indep5d5t ( ! size ( ! object-glass4 ,! diff]5ce may be readily te/$4 ,if we direct an op]a-glass ^u any object1 we %all f9d t any cov]+ plac$ ov] a "p ( ! object-glass becomes visible :5 we look ?r\gh ! in/rum5t1 int]f]+ !re=e pro tanto ) ! range ( view4 ,a cov]+ simil>ly plac$ on any "p ( ! object-glass ( an a/ronomical telescope does n become visible :5 we look ?r\gh ! in/rum5t4 ,! di/9ction has a v important be>+ on ! !ory ( telescopic vision4 ,9 consid]+ ! application ( ! telescope to practical obs]vation1 ! circum/ance t 9 ! ,galilean ,telescope no real image is =m$1 is yet m important4 ,a real image admits ( measurem5t1 l9e> or angul>1 :ile to a virtual image 7su* an image1 = in/ance1 z is =m$ by a common look+-glass7 no su* process c be appli$4 ,9 simple obs]vation ! only noticeable effect ( ?is diff]5ce is t1 :]eas 9 ! a/ronomical ,telescope a /op or diaphragm c be ins]t$ 9 ! tube s z to cut (f :at is call$ ! ragg$ edge ( ! field ( view 7:i* includes all ! "p n rea*$ by full p5cils ( light f ! object-glass71 !re is no means ( rem$y+ ! correspond+ defect 9 ! ,galilean ,telescope4 ,x w\ld be a v annoy+ defect 9 a telescope int5d$ = a/ronomical obs]vation1 s9ce 9 g5]al ! edge ( ! field ( view is n p]ceptible at night4 ,! unpleasant nature ( ! defect may be se5 by look+ ?r\gh an op]a-glass1 & notic+ ! gradual fad+ away ( light r\nd ! circumf]5ce ( ! field ( view4 ,! prop]ties ( reflection z well z ( refraction h be5 enli/$ into ! s]vice ( ! a/ronomical obs]v]4 ,! =mation ( an image by means ( a concave mirror is exhibit$ 9 fig4 #c4 ,z ! obs]v]'s head w\ld be plac$ betwe5 ! object & ! mirror1 if ! image1 =m$ z 9 fig4 #c1 7 to be microscopically exam9$1 v>i\s devices are employ$ 9 ! con/ruction ( reflect+ telescopes to avoid ! loss ( light :i* w\ld result--a loss :i* w\ld be important ev5 ) ! l>ge/ mirrors yet con/ruct$4 ,?us1 9 ,gregory's ,telescope1 a small mirror1 hav+ its concavity t[>ds ! great "o1 is plac$ 9 ! axis ( ! tube & =ms an image :i* is view$ ?r\gh an ap]ture 9 ! middle ( ! great mirror4 ,a simil> plan is adopt$ 9 ,cassegra9's ,telescope1 a small convex mirror replac+ ! concave "o4 ,9 ,newton's ,telescope a small incl9$-plane reflector is us$1 :i* s5ds ! p5cil ( light (f at "r-angles to ! axis ( ! tube4 ,9 ,h]s*el's ,telescope ! great mirror is incl9$ s t ! image is =m$ at a slight di/ance f ! axis ( ! telescope4 ,9 ! two fir/ cases ! object is view$ 9 ! usual or direct way1 ! image be+ erect 9 ,gregory's & inv]t$ 9 ,cassegra9's4 ,9 ! ?ird ! obs]v] looks ?r\gh ! side ( ! telescope1 see+ an inv]t$ image ( ! object4 ,9 ! la/ ! obs]v] sees ! object inv]t$1 b n alt]$ z respects "r & left4 ,! la/-m5tion$ me?od ( view+ objects is ! only "o 9 :i* ! obs]v]'s back is turn$ t[>ds ! object1 yet ?is me?od is call$ ! front view--app>5tly quasi lucus a non luc5do4 ,illu/ration3 ,fig4 #c4 ,x appe>s1 !n1 t 9 all a/ronomical ,telescopes1 reflect+ or refract+1 a real image ( an object is submitt$ to microscopical exam9ation4 ,( ?is fact ! possessor ( a telescope may easily assure himself2 = if ! eye-glass be remov$1 & a small scre5 be plac$ at ! focus ( ! object-glass1 !re w appe> ^u ! scre5 a small picture ( any object t[>ds :i* ! tube is turn$4 ,b ! image may be view$ 9 ano!r way :i* requires to be notic$4 ,if ! eye1 plac$ at a di/ance ( five or six in*es f ! image1 be direct$ d[n ! tube1 ! image w be se5 z be=e2 9 fact1 j z a s+le convex l5s ( %ort focus is ! simple/ microscope1 s a simple convex l5s ( long focus is ! simple/ telescope4#a ,b a s+ul> circum/ance w imm$iately attract ! obs]v]'s notice4 ,a real picture1 or ! image =m$ on ! scre5 z 9 ! =m] case1 c be view$ at v>y+ di/ances2 b :5 we view ! image directly1 x w be f\nd t = di/9ct vision ! eye mu/ be plac$ almo/ exactly at a fix$ di/ance f ! image4 ,?is peculi>ity is m important ?an x might be ?\ght at fir/ sight4 ,9 fact1 x is ess5tial t ! obs]v] :o w\ld rightly apply ! p[]s ( 8 telescope1 or fairly te/ its p]=mance1 %\ld und]/& 9 :at respect an image =m$ by an object-glass or object-mirror diff]s f a real object4 ,! peculi>ities to be not$ are ! curvature1 indi/9ctness1 & false col\r+ ( ! image4 ,! curvature ( ! image is ! lea/ important ( ! ?ree defects nam$--a =tunate circum/ance1 s9ce ?is defect admits nei!r ( rem$y nor modification4 ,! image ( a di/ant object1 in/ead ( ly+ 9 a plane1 t is1 =m+ :at is te*nically call$ a flat field1 =ms "p ( a sph]ical surface ^: c5tre is at ! c5tre ( ! object-glass4 ,h5ce ! c5tre ( ! field ( view is some:at ne>] to ! eye ?an are ! out] p>ts ( ! field4 ,! am\nt ( curvature cle>ly dep5ds on ! ext5t ( ! field ( view1 & !re=e is n great 9 p[]ful telescopes4 ,?us1 if we suppose t ! angul> ext5t ( ! field is ab\t half a degree 7a l>ge or l[-p[] field71 ! c5tre is ne>] ?an ! b\nd>y ( ! field by ab\t #a-cbj? "p only ( ! field's diamet]4 ,! indi/9ctness ( ! image is p>tly due to ! obliquity ( ! p5cils :i* =m p>ts ( ! image1 & p>tly to :at is t]m$ sph]ical ab]ration4 ,! fir/ cause _c be modifi$ by ! optician's skill1 & is n important :5 ! field ( view is small4 ,sph]ical ab]ration causes ^? p>ts ( a p5cil :i* fall ne> ! b\nd>y ( a convex l5s to conv]ge to a ne>] 7i4e4 %ort]7 focus ?an ^? :i* fall ne> ! c5tre4 ,?is may be correct$ by a prop] selection ( ! =ms ( ! two l5ses :i* replace1 9 all mod]n telescopes1 ! s+le l5s hi!rto consid]$4 ,! false col\r+ ( ! image is due to *romatic ab]ration4 ,! p5cil ( light proce$+ f a po9t1 conv]ges1 n to "o po9t1 b to a %ort l9e ( v>y+ col\r4 ,?us a s]ies ( col\r$ images is =m$1 at diff]5t di/ances f ! object-glass4 ,s t1 if a scre5 7 plac$ to receive ! mean image 9 focus1 a col\r$ fr+e due to ! o!r images 7out ( focus1 & !re=e too l>ge7 w\ld surr\nd ! mean image4 ,newton suppos$ t x 0 impossible to get rid ( ?is defect1 & !re=e turn$ 8 att5tion to ! con/ruction ( reflectors4 ,b ! discov]y t ! disp]sive p[]s ( diff]5t glasses are n proportional to _! reflective p[]s1 suppli$ opticians ) ! means ( rem$y+ ! defect4 ,let u cle>ly und]/& :at is ! discov]y ref]r$ to4 ,if ) a glass prism ( a c]ta9 =m we produce a spectrum ( ! sun1 ?is spectrum w be ?r[n a c]ta9 di/ance away f ! po9t on :i* ! sun's rays w\ld fall if n int]f]$ )4 ,?is di/ance dep5ds on ! refractive p[] ( ! glass4 ,! spectrum w h a c]ta9 l5g?1 dep5d+ on ! disp]sive p[] ( ! glass4 ,n[1 if we *ange our prism = ano!r ( exactly ! same %ape1 b made ( a diff]5t k9d ( glass1 we %all f9d ! spectrum ?r[n to a diff]5t spot4 ,if x appe>$ t ! l5g? ( ! new spectrum 0 increas$ or dim9i%$ 9 exactly ! same proportion z its di/ance f ! l9e ( ! sun's direct light1 x w\ld h be5 hopeless to attempt to rem$y *romatic ab]ration4 ,newton took x = grant$ t ?is 0 s4 ,b ! exp]im5ts ( ,hall & ! ,dollonds %[$ t !re is no su* /rict proportionality betwe5 ! disp]sive & refractive p[]s ( diff]5t k9ds ( glass4 ,x accord+ly becomes possible to correct ! *romatic ab]ration ( "o glass by sup]add+ t ( ano!r4 ,illu/ration3 ,fig4 #d4 ,?is is effect$ by comb9+1 z %[n 9 fig4 #d1 a convex l5s ( cr[n glass ) a concave l5s ( fl9t glass1 ! convex l5s be+ plac$ ne>e/ to ! object4 ,a little col\r /ill rema9s1 b n en\gh to int]f]e s]i\sly ) ! di/9ctness ( ! image4 ,b ev5 if ! image =m$ by ! object-glass 7 p]fect1 yet ?is image1 view$ ?r\gh a s+le convex l5s ( %ort focus plac$ z 9 fig4 #a1 w\ld appe> curv$1 indi/9ct1 col\r$1 & also di/ort$1 because view$ by p5cils ( light :i* d n pass ?r\gh ! c5tre ( ! eye-glass4 ,^! effects c be dim9i%$ 7b n entirely remov$ toge!r7 by us+ an eye-piece consi/+ ( two l5ses in/ead ( a s+le eye-glass4 ,! two =ms ( eye-piece mo/ commonly employ$ are exhibit$ 9 figs4 #e & #f4 ,fig4 #e is ,huygh5s' eye-piece1 call$ also ! negative eye-piece1 because a real image is =m$ beh9d ! field-glass 7! l5s :i* lies ne>e/ to ! object-glass74 ,fig4 #f repres5ts ,ramsd5's eye-piece1 call$ also ! positive eye-piece1 because ! real image =m$ by ! object-glass lies 9 front ( ! field-glass4 ,illu/ration3 ,fig4 #e4 ,illu/ration3 ,fig4 #f4 ,! c\rse ( a slightly oblique p5cil ?r\gh ei!r eye-piece is exhibit$ 9 ! figures4 ,! l5ses are usually plano-convex1 ! convexities be+ turn$ t[>ds ! object-glass 9 ! negative eye-piece1 & t[>ds ea* o!r 9 ! positive eye-piece4 ,codd+ton has %[n1 h[ev]1 t ! be/ =ms = ! l5ses ( ! negative eye-piece are ^? %[n 9 fig4 #e4 ,! negative eye-piece1 be+ a*romatic1 is commonly employ$ 9 all obs]vations requir+ di/9ct vision only4 ,b z x is cle>ly unfit = obs]vations requir+ micrometrical measurem5t1 or ref]5ce to fix$ l9es at ! focus ( ! object-glass1 ! positive eye-piece is us$ = ^! purposes4 ,= obs]v+ objects at great elevations ! diagonal eye-tube is (t5 conv5i5t4 ,its con/ruction is %[n 9 fig4 #g4 ,,abc is a totally reflect+ prism ( glass4 ,! rays f ! object-glass fall on ! face ,,ab1 are totally reflect$ on ! face ,,bc1 & em]ge ?r\gh ! face ,,ac4 ,9 us+ ?is eye-piece1 x mu/ be rememb]$ t x l5g!ns ! slid+ eye-tube1 :i* mu/ !re=e be ?ru/ fur!r 91 or ! object w n be se5 9 focus4 ,!re is an arrangem5t by :i* ! *ange ( direction is made to take place betwe5 ! two glasses ( ! eye-piece4 ,) ?is arrangem5t 7kn[n z ! diagonal eye-piece7 no adju/m5t ( ! eye-tube is requir$4 ,h[ev]1 = amateurs' telescopes ! m conv5i5t arrangem5t is ! diagonal eye-tube1 s9ce x enables ! obs]v] to apply any eye-piece he *ooses1 j z ) ! simple slid+ eye-tube4 ,illu/ration3 ,fig4 #g4 ,we come next to ! important "q ( ! m\nt+ ( our telescope4 ,! be/ kn[n1 &1 9 "s respects1 ! simple/ me?od ( m\nt+ a telescope = g5]al obs]vation is t kn[n z ! altitude-&-azimu? m\nt+4 ,9 ?is me?od ! telescope is po9t$ t[>ds an object by two motions1--"o giv+ ! tube ! requir$ altitude 7or elevation71 ! o!r giv+ x ! requir$ azimu? 7or direction z respects ! compass po9ts74 ,= small alt-azimu?s ! ord9>y pill>-&-claw /& is suffici5tly /eady4 ,= l>g] in/rum5ts o!r arrangem5ts are ne$$1 bo? to give ! telescope /ead9ess1 & to supply sl[ movem5ts 9 altitude & azimu?4 ,! /ud5t w f9d no difficulty 9 und]/&+ ! arrangem5t ( slid+-tubes & rack-"w commonly adopt$4 ,?is arrangem5t seems to me to be 9 _m respects defective1 h[ev]4 ,! sl[ movem5t 9 altitude is n uni=m1 b v>ies 9 effect accord+ to ! elevation ( ! object obs]v$4 ,x is also limit$ 9 range2 & q a little s]ies ( op]ations has to be gone ?r\gh :5 x is requir$ to direct ! telescope t[>ds a new qu>t] ( ! heav5s4 ,h[ev] exp]t ! obs]v] may become by practice 9 effect+ ^! op]ations1 !y necess>ily take up "s "t 7p]=m$ z !y mu/ be 9 ! d>k1 or by ! light ( a small lant]n71 & dur+ ?is "t x (t5 happ5s t a fav\rable opportunity = obs]vation is lo/4 ,^! disadvantages are obviat$ :5 ! telescope is m\nt$ 9 su* a mann] z is exhibit$ 9 fig4 #h1 :i* repres5ts a telescope ( my own con/ruction4 ,! sl[ movem5t 9 altitude is giv5 by rotat+ ! rod he1 ! endless screw 9 :i* turns ! small :eel at b1 ^: axle 9 turn be>s a p9ion-:eel work+ 9 ! tee? ( ! quadrant a4 ,! sl[ movem5t 9 azimu? is giv5 9 l mann] by rotat+ ! rod h'e'1 ! lant]n-:eel at ! end ( :i* turns a cr[n-:eel on ^: axle is a p9ion-:eel work+ 9 ! tee? ( ! circle c4 ,! cas+s at e & e'1 9 :i* ! rods he & h'e' respectively "w1 are s fa/5$ by ela/ic cords t an upw>d pressure on ! h&le h1 or a d[nw>d pressure on ! h&le h'1 at once releases ! endless screw or ! cr[n-:eel respectively1 s t ! telescope c be swept at once ?r\gh any desir$ angle 9 altitude or azimu?4 ,?is me?od ( m\nt+ has o!r advantages2 ! h&les are conv5i5tly situat$ & con/ant 9 position2 also1 z !y d n "w directly on ! telescope1 !y c be turn$ )\t sett+ ! tube 9 vibration4 ,illu/ration3 ,fig4 #h4 ,i d n recomm5d ! m\nt+ to be exactly z %[n 9 fig4 #h4 ,t me?od is mu* too exp5sive = an alt-azimu?4 ,b a simple arrangem5t ( belt$ :eels 9 place ( ! too!d :eels a & c might v readily be prep>$ by ! +5i\s amateur telescopi/2 & ,i feel c]ta9 t ! com=t & conv5i5ce ( ! arrangem5t w\ld amply repay him = ! lab\r x w\ld co/ him4 ,my own telescope--?\gh ! l>ge too!d-:eel & ! quadrant 7 made inconv5i5tly heavy 7?r\gh a mi/ake ( ! workman :o con/ruct$ ! in/rum5t7--work$ z easily & almo/ z conv5i5tly z an equatorial4 ,/ill1 x is well = ! obs]v] :o wi%es sy/ematically to survey ! heav5s--& :o c af=d ! exp5se--to obta9 a well-m\nt$ equatorial4 ,9 ?is me?od ( m\nt+1 ! ma9 axis is direct$ to ! pole ( ! heav5s2 ! o!r axis1 at "r angles to ! fir/1 c>ries ! telescope-tube4 ,"o ( ! _m me?ods adopt$ = m\nt+ equatorials is t exhibit$--) ! omission ( "s m9or details--9 fig4 #i4 a is ! pol> axis1 b is ! axis 7call$ ! decl9ation axis7 :i* be>s ! telescope4 ,! circles c & d s]ve to indicate1 by means ( v]ni]s revolv+ ) ! axes1 ! motion ( ! telescope 9 "r asc5sion & decl9ation1 respectively4 ,! weight w s]ves to c\nt]poise ! telescope1 & ! screws s1 s1 s1 s1 s]ve to adju/ ! in/rum5t s t ! pol> axis %all be 9 its prop] position4 ,! advantage ga9$ by ! equatorial me?od ( m\nt+ is t only "o motion is requir$ to foll[ a />4 ,ow+ to ! diurnal rotation ( ! e>?1 ! />s appe> to move uni=mly 9 circles p>allel to ! cele/ial equator2 & x is cle> t a /> s mov+ w be kept 9 ! field ( view1 if ! telescope1 once direct$ to ! />1 be made to revolve uni=mly & at a prop] rate r\nd ! pol> axis4 ,illu/ration3 ,fig4 #i4 ,! equatorial c be direct$ by means ( ! circles c & d to any cele/ial object ^: "r asc5sion & decl9ation are kn[n4 ,on ! o!r h&1 to br+ an object into ! field ( view ( an alt-azimu?1 x is necess>y1 ei!r t ! object itself %\ld be visible to ! nak$ eye1 or else t ! position ( ! object %\ld be pretty accurately le>n$ f />-maps1 s t x may be pick$ up by ! alt-azimu? aft] a little se>*+4 ,a small telescope call$ a f9d] is usually atta*$ to all p[]ful telescopes int5d$ = g5]al obs]vation4 ,! f9d] has a l>ge field ( view1 & is adju/$ s z to h its axis p>allel to t ( ! l>ge telescope4 ,?us a /> br\ght to ! c5tre ( ! l>ge field ( ! f9d] 7indicat$ by ! int]section ( two l9es plac$ at ! focus ( ! eye-glass7 is at1 or v ne>1 ! c5tre ( ! small field ( ! l>ge telescope4 ,if a telescope has no f9d]1 x w be easy = ! /ud5t to con/ruct "o = himself1 & w be a useful ex]cise 9 optics4 ,two convex l5ses n v diff]5t 9 size f ^? %[n 9 fig4 #a1 & plac$ z !re %[n--! di/ance betwe5 !m be+ ! sum ( ! focal l5g?s ( ! two glasses--9 a small tube ( c>d1 wood1 or t91 w s]ve ! purpose ( a f9d] = a small telescope4 ,x c be atta*$ by wires to ! telescope-tube1 & adju/$ ea* night be=e comm5c+ obs]vation4 ,! adju/m5t is ?us manag$3--a l[ p[] be+ appli$ to ! telescope1 ! tube is turn$ t[>ds a bright />2 ?is is easily effect$ ) a l[ p[]2 !n ! f9d] is to be fix$1 by means ( its wires1 9 su* a position t ! /> %all be 9 ! c5tre ( ! field ( ! f9d] :5 also 9 ! c5tre ( ! telescope's field4 ,:5 ?is has be5 done1 ! f9d] w greatly help ! obs]vations ( ! ev5+2 s9ce ) high p[]s mu* "t w\ld be wa/$ 9 br++ an object into ! field ( view ( ! telescope )\t ! aid ( a f9d]4 ,yet m "t w\ld be wa/$ 9 ! case ( an object n visible to ! nak$ eye1 b ^: position ) ref]5ce to sev]al visible />s is kn[n2 s9ce1 :ile x is easy to br+ ! po9t requir$ to ! c5tre ( ! f9d]'s field1 9 :i* ! guid+ />s are visible1 x is v difficult to direct ! telescope's tube on a po9t ( ?is sort4 ,a c>d tube ) wire fa/5+s1 su* z we h describ$1 may appe> a v insignificant contrivance to ! regul> obs]v]1 ) 8 well-m\nt$ equatorial & c>efully-adju/$ f9d]4 ,b to ! fir/ attempts ( ! amateur obs]v] x af=ds no insignificant assi/ance1 z ,i c av] f my own exp]i5ce4 ,)\t x--a sup]ior f9d] be+ want+--our half-h\rs w\ld soon be wa/$ away 9 t mo/ we>isome & annoy+ ( all employm5ts1 try+ to pick up cele/ial objects4 ,x behoves me at ?is po9t to speak ( />-maps4 ,su* maps are ( _m diff]5t k9ds4 ,!re are ! ,obs]vatory maps1 9 :i* ! places ( ?\s&s ( />s are record$ ) an amaz+ accuracy4 ,our beg9n] is n likely to make use (1 or to want1 su* maps z ^!4 ,!n !re are maps m]ely int5d$ to give a good g5]al idea ( ! appe>ance ( ! heav5s at diff]5t h\rs & seasons4 ,plate ,i4 pres5ts f\r maps ( ?is sort2 b a m complete s]ies ( eight maps has be5 publi%$ by ,messrs4 ,walton & ,mab]ly 9 an octavo "w2 & my own ',con/ellation-,seasons' give1 at ! same price1 twelve qu>to maps 7( f\r ( :i* ^? 9 ,plate ,i4 are m9iatures71 %[+ ! appe>ance ( ! sky at any h\r f mon? to mon?1 or on any night1 at successive int]vals ( two h\rs4 ,b maps int]m$iate 9 "* to ^! & to ,obs]vatory maps are requir$ by ! amateur obs]v]4 ,su* are ! ,society's six gnomonic maps1 ! set ( six gnomonic maps 9 ,john/one's ',atlas ( ,a/ronomy1' & my own set ( twelve gnomonic maps4 ,! ,society's maps are a rem>kably good set1 conta9+ on ! scale ( a t5-in* globe all ! />s 9 ! ,catalogue ( ! ,a/ronomical ,society 7d[n to ! fif? magnitude74 ,! di/ortion1 h[ev]1 is necess>ily enorm\s :5 ! cele/ial sph]e is pres5t$ 9 only six gnomonic maps4 ,9 my maps all ! />s ( ! ,briti% ,association ,catalogue d[n to ! fif? magnitude are includ$ on ! scale ( a six-in* globe4 ,! di/ortion is sc>cely a f\r? ( t 9 ! ,society's maps4 ,! maps are s arrang$ t ! relative positions ( all ! />s 9 ea* hemisph]e c be readily ga!r$ f a s+le view2 & black duplicate-maps s]ve to %[ ! appe>ance ( ! con/ellations4 ,x is (t5 conv5i5t to make small maps ( a "p ( ! heav5s we may wi% to /udy closely4 ,my ',h&book ( ! ,/>s' has be5 prep>$ to aid ! /ud5t 9 ! con/ruction ( su* maps4 ,9 select+ maps x is well to be able to recognise ! am\nt ( di/ortion & scale-v>iation4 ,?is may be done by exam9+ ! spaces includ$ betwe5 successive p>allels & m]idians1 ne> ! edges & angles ( ! maps1 & comp>+ ^! ei!r ) ^? 9 ! c5tre ( ! map1 or ) ! kn[n figures & dim5sions ( ! correspond+ spaces on a globe4 ,we may n[ proce$ to discuss ! diff]5t te/s :i* ! int5d+ pur*as] ( a telescope %\ld apply to ! in/rum5t4 ,! excell5ce ( an object-glass c be satisfactorily det]m9$ only by te/+ ! p]=mance ( ! telescope 9 ! mann] pres5tly to be describ$4 ,b x is well to exam9e ! quality ( ! glass z respects transp>5cy & uni=mity ( texture4 ,bubbles1 scrat*es1 & o!r su* defects1 are n v important1 s9ce !y d n affect ! di/9ctness ( ! field z !y w\ld 9 a ,galilean ,telescope1--a little light is lo/1 & t is all4 ,! same rem>k applies to du/ ^u ! glass4 ,! glass %\ld be kept z free z possible f dirt1 damp1 or du/1 b x is n advisable to remove e speck :i*1 despite su* precaution1 may accid5tally fall ^u ! object-glass4 ,:5 x becomes necess>y to clean ! glass1 x is to be not$ t ! sub/ance us$ %\ld be s(t1 p]fectly dry1 & free f du/4 ,silk is (t5 recomm5d$1 b "s silk is exce$+ly objectionable 9 texture1--old silk1 p]fectly s(t to ! t\*1 is p]haps z good z any?+4 ,if ! du/ :i* has fall5 on ! glass is at all gritty1 ! glass w suff] by ! me?od ( clean+ commonly adopt$1 9 :i* ! du/ is ga!r$ up by pressure4 ,! prop] me?od is to clean a small space ne> ! edge ( ! glass1 & to sweep f t space z c5tre4 ,9 ?is way ! du/ is pu%$ be=e ! silk or wa%-lea!r1 & does n cut ! glass4 ,x is well always to suspect ! pres5ce ( gritty du/1 & adopt ?is cauti\s me?od ( clean+4 ,! two glasses %\ld on no acc\nt be sep>at$4 ,9 exam9+ an eye-piece1 ! quality ( ! glass %\ld be not$1 & c>e tak5 t bo? glasses 7b especially ! field-glass7 are free f ! lea/ speck1 scrat*1 or blemi% ( any k9d1 = ^! defects w be exhibit$ 9 a magnifi$ /ate 9 ! field ( view4 ,h5ce ! eye-pieces require to be z c>efully pres]v$ f damp & du/ z ! object-glass1 & to be m frequ5tly clean$4 ,! tube ( ! telescope %\ld be light1 b /rong1 & free f vibration4 ,its quality 9 ! la/ respect c be te/$ by lightly /rik+ x :5 m\nt$2 ! s\nd giv5 out %\ld be dead or non-resonant4 ,! inside ( ! tube mu/ absorb extrane\s light1 & %\ld !re=e be col\r$ a dull black2 & /ops ( v>y+ radius %\ld be plac$ along its l5g? ) ! same object4 ,slid+ tubes1 rack-"w1 etc41 %\ld "w closely1 yet easily4 ,! telescope %\ld be well balanc$ = vision ) ! small a/ronomical eye-pieces4 ,b z !re is (t5 occasion to use appliances :i* di/urb ! balance1 x is well to h ! means ( at once re/or+ equilibrium4 ,a cord r+ runn+ r\nd ! tube 7pretty tightly1 s z to re/ /ill :5 ! tube is incl9$71 & be>+ a small weight1 w be all t is requir$ = ?is purpose2 x mu/ be slipp$ along ! tube until ! tube is f\nd to be p]fectly balanc$4 ,no?+ is m annoy+ ?an1 aft] gett+ a /> well 9 ! field1 to see ! tube %ift its position ?r\gh defective balance1 & ?us to h to se>* aga9 = ! />4 ,ev5 ) su* an arrangem5t z is %[n 9 fig4 #h1 ?\gh ! tube _c readily %ift its position1 x is bett] to h x well balanc$4 ,! quality ( ! /& has a v important influ5ce on ! p]=mance ( a telescope4 ,9 fact1 a mod]ately good telescope1 m\nt$ on a /eady /&1 work+ easily & conv5i5tly1 w n only enable ! obs]v] to pass 8 "t mu* m pleasantly1 b w absolutely exhibit m difficult objects ?an a f9] in/rum5t on a rickety1 ill-arrang$ /&4 ,a good obs]v+-*air is also a matt] ( "s importance1 ! lea/ con/ra9t or awkw>dness ( position detract+ consid]ably f ! p[] ( di/9ct vision4 ,su*1 at lea/1 is my own exp]i5ce4 ,b ! m]e exam9ation ( ! glasses1 tube1 m\nt+1 c41 is only ! fir/ /ep 9 ! s]ies ( te/s :i* %\ld be appli$ to a telescope1 s9ce ! excell5ce ( ! in/rum5t dep5ds1 n on its size1 ! beauty ( its m\nt+1 or any extrane\s circum/ances1 b on its p]=mance4 ,! obs]v] %\ld fir/ det]m9e :e!r ! *romatic ab]ration is correct$4 ,to asc]ta9 ?is ! telescope %\ld be direct$ to ! moon1 or 7bett]7 to ,jupit]1 & accurately focuss$ = di/9ct vision4 ,if1 !n1 on mov+ ! eye-piece t[>ds ! object-glass1 a r+ ( purple appe>s r\nd ! m>g9 ( ! object1 & on mov+ ! eye-glass 9 ! contr>y direction a r+ ( gre51 ! *romatic ab]ration is correct$1 s9ce ^! are ! col\rs ( ! second>y spectrum4 ,to det]m9e :e!r ! sph]ical ab]ration is correct$1 ! telescope %\ld be direct$ t[>ds a /> ( ! ?ird or f\r? magnitude1 & focuss$ = di/9ct vision4 ,a cap ) an ap]ture ( ab\t "o-half its diamet] %\ld !n be plac$ ov] ! object-glass4 ,if no new adju/m5t is requir$ = di/9ct vision1 ! sph]ical ab]ration is correct$1 s9ce ! mean focal l5g? & ! focal l5g? ( ! c5tral rays are equal4 ,if1 :5 ! cap is on1 ! eye-piece has to be pull$ out = di/9ct vision1 ! sph]ical ab]ration has n be5 fully correct$2 if ! eye-piece has to be pu%$ 91 ! ab]ration has be5 ov]-correct$4 ,z a fur!r te/1 we may cut (f ! c5tral rays1 by means ( a circul> c>d cov]+ ! middle ( ! object-glass1 & comp>e ! focal l5g? = di/9ct vision ) ! focal l5g? :5 ! cap is appli$4 ,! ext5t ( ! sph]ical ab]ration may be ?us det]m9$2 b if ! fir/ exp]im5t gives a satisfactory result1 no o!r is requir$4 ,a /> ( ! fir/ magnitude %\ld next be br\ght into ! field ( view4 ,if an irradiation f "o side is p]ceiv$1 "p ( ! object-glass has n ! same refractive p[] z ! re/2 & ! "p :i* is defective c be det]m9$ by apply+ 9 diff]5t positions a cap :i* hides half ! object-glass4 ,if ! irradiation is d\ble1 x w probably be f\nd t ! object-glass has be5 too tightly screw$1 & ! defect w disappe> :5 ! glass is fre$ f su* undue pressure4 ,if ! object-glass is n q at "r angles to ! axis ( ! tube1 or if ! eye-tube is at all incl9$1 a l irradiation w appe> :5 a bright /> is 9 ! field4 ,! =m] defect is n easily detect$ or rem$i$2 nor is x commonly met ) 9 ! "w ( a c>eful optician4 ,! latt] defect may be detect$ by cutt+ out ?ree circul> c>ds ( suitable size ) a small ap]ture at ! c5tre ( ea*1 & ins]t+ "o at ea* end ( ! eye-tube1 & "o ov] ! object-glass4 ,if ! tube is rightly plac$ ! ap]tures w ( c\rse lie 9 a "r l9e1 s t x w be possible to look ?r\gh all ?ree at once4 ,if n1 x w be easy to det]m9e t[>ds :at "p ( ! object-glass ! eye-tube is direct$1 & to correct ! position ( ! tube accord+ly4 ,! be/ te/s = det]m9+ ! def9+ p[] ( a telescope are close d\ble or multiple />s1 ! compon5ts ( :i* are n v unequal4 ,! illum9at+ p[] %\ld be te/$ by direct+ ! telescope t[>ds d\ble or multiple />s hav+ "o or m m9ute compon5ts4 ,_m ( ! nebul s]ve z te/s bo? = illum9ation & def9+ p[]4 ,z we proce$ we %all meet ) prop] objects = te/+ diff]5t telescopes4 ,= ! pres5t1 let ! foll[+ li/ suffice4 ,x is select$ f ,admiral ,smy?'s te/s1 obta9$ by dim9i%+ ! ap]ture ( a #f-;94 telescope hav+ a focal l5g? ( #h-a_/b feet3 ,a two-in* ap]ture1 ) p[]s ( f #fj to #ajj1 %\ld exhibit alpha ,piscium 7#ce74 delta ,cassiopei 7#ie71 mag4 7#d & #g-a_/b7 gamma ,leonis 7#cb74 ,pol>is 7#ahf71 mag4 7#b-a_/b & #i-a_/b7 ,a f\r-in*1 p[]s #hj to #abj1 %\ld exhibit xi ,urs ,majoris 7#bd74 sigma ,cassiopei 7#ca71 mag4 7#f & #h74 gamma ,ceti 7#bf74 delta ,gem9orum 7#ga71 mag4 7#d & #i74 ,! te/s 9 ! fir/ column are = def9ition1 ^? 9 ! second = illum9ation4 ,x w be notic$ t1 ?\gh 9 ! case ( ,pol>is ! small] ap]ture may be expect$ to %[ ! small /> ( less ?an ! #i? magnitude1 a l>g] ap]ture is requir$ to %[ ! #h? magnitude compon5t ( sigma ,cassiopei1 on acc\nt ( ! great] clos5ess ( ?is d\ble4 ,9 fav\rable wea!r ! foll[+ is a good g5]al te/ ( ! p]=mance ( a telescope3--,a /> ( ! #crd or #d? magnitude at a consid]able elevation above ! horizon %\ld exhibit a small well def9$ disc1 surr\nd$ by two or ?ree f9e r+s ( light4 ,a telescope %\ld n be m\nt$ )9 doors1 if x c be conv5i5tly erect$ on solid gr\nd1 z e movem5t 9 ! h\se w cause ! in/rum5t to vibrate unpleasantly4 ,fur!r1 if ! telescope is plac$ 9 a w>m room1 curr5ts ( cold air f )\t w r5d] obs]v$ objects hazy & indi/9ct4 ,9 fact1 ,sir ,w4 ,h]s*el consid]$ t a telescope %\ld n ev5 be erect$ ne> a h\se or elevation ( any k9d r\nd :i* curr5ts ( air are likely to be produc$4 ,if a telescope is us$ 9 a room1 ! temp]ature ( ! room %\ld be made z ne>ly equal z possible to t ( ! out] air4 ,:5 a telescope is us$ out ( doors a 'dew-cap1' t is1 a tube ( t9 or pa/ebo>d1 "s t5 or twelve in*es long1 %\ld be plac$ on ! end ( ! in/rum5t1 s z to project beyond ! object-glass4 ,= glass is a good radiator ( heat1 s t dew falls heavily ^u x1 unless ! radiation is 9 "s way *eck$4 ,! dew-cap does ?is effectually4 ,x %\ld be black5$ )91 especially if made ( metal4 ,aft] use1 says old ,kit*5]1 ! telescope %\ld be kept 9 a w>m place long en\gh = any moi/ure on ! object-glass to evaporate4 ,if damp gets betwe5 ! glasses x produces a fog 7:i* opticians call a sweat7 or ev5 a seawe$-l vegetation1 by :i* a valuable glass may be completely ru9$4 ,! obs]v] %\ld n leave to ! preci\s h\rs ( ! night ! /udy ( ! be>+ & position ( ! objects he proposes to exam9e4 ,?is %\ld be done by day--an arrangem5t :i* has a tw(old advantage1--! "t available = obs]vation is l5g!n$1 & ! eyes are sp>$ sudd5 *anges f d>kness to light1 & vice v]s4 ,besides1 ! eye is ill-fitt$ to exam9e difficult objects1 aft] se>*+ by c&le-light among/ ! m9ute details record$ 9 maps or globes4 ,( ! effect ( re/ to ! eye we h an in/ance 9 ,sir ,j4 ,h]s*el's r$iscov]y ( ! satellites ( ,uranus1 :i* he effect$ aft] keep+ 8 eyes 9 d>kness = a qu>t] ( an h\r4 ,kit*5]1 inde$1 goes s f> z to recomm5d 7) a cr$e exp]to7 an int]val ( sleep 9 ! d>kness ( ! obs]v+-room be=e comm5c+ op]ations4 ,i h nev] tri$ ! exp]im5t1 b ,i %\ld expect x to h a bad r ?an a good effect on ! eyesight1 z "o commonly sees ! eyes ( a p]son :o has be5 sleep+ 9 8 day-clo!s look heavy & blood%ot4 ,! object or ! "p ( an object to be obs]v$ %\ld be br\ght z ne>ly z possible to ! c5tre ( ! field ( view4 ,:5 !re is no app>atus = keep+ ! telescope po9t$ ^u an object1 ! be/ plan is s to direct ! telescope by means ( ! f9d]1 t ! object %all be j out ( ! field ( view1 & be br\ght 7by ! e>?'s motion7 across ! c5tre ( ! field4 ,?us ! vibrations :i* always foll[ ! adju/m5t ( ! tube w h subsid$ be=e ! object appe>s4 ,! object %\ld !n be int5tly wat*$ dur+ ! :ole int]val ( its passage across ! field ( view4 ,x is important t ! /ud5t %\ld recognise ! fact t ! highe/ p[]s d n necess>ily give ! be/ views ( cele/ial objects4 ,high p[]s 9 all cases increase ! difficulty ( obs]vation1 s9ce !y dim9i% ! field ( view & ! illum9ation ( ! object1 increase ! motion ) :i* 7ow+ to ! e>?'s motion7 ! image moves across ! field1 & magnify all defects due to in/ability ( ! /&1 imp]fection ( ! object-glass1 or undulation ( ! atmosph]e4 ,a good object-glass ( ?ree in*es ap]ture w 9 v fav\rable wea!r be> a p[] ( ab\t #cjj1 :5 appli$ to ! obs]vation ( close d\ble or multiple />s1 b = all o!r obs]vations mu* l[] p[]s %\ld be us$4 ,no?+ b failure & annoyance c foll[ ! attempt to employ ! highe/ p[]s on unsuitable objects or 9 unfav\rable wea!r4 ,! greate/ c>e %\ld be tak5 9 focuss+ ! telescope4 ,:5 high p[]s are us$ ?is is a matt] ( "s delicacy4 ,x w\ld be well if ! eye-pieces int5d$ = a telescope 7 s con/ruct$ t :5 ! telescope is focuss$ = "o1 ?is might be replac$ by any o!r )\t necessitat+ any use ( ! focuss+ rack-"w4 ,?is c\ld be readily effect$ by suitably plac+ ! %\ld] :i* limits ! ins]tion ( ! eye-piece4 ,x w be f\nd t1 ev5 9 ! wor/ wea!r = obs]vation1 !re are in/ants ( di/9ct vision 7) mod]ate p[]s7 dur+ :i* ! c>eful obs]v] may cat* sight ( important details2 &1 simil>ly1 9 ! be/ obs]v+ wea!r1 !re are mom5ts ( unusually di/9ct vision well wor? pati5t wait+ =1 s9ce 9 su* wea!r alone ! full p[]s ( ! telescope c be employ$4 ,! telescopi/ %\ld n be det]r$ f obs]vation by ! pres5ce ( fog or haze1 s9ce ) a hazy sky def9ition is (t5 s+ul>ly good4 ,! obs]v] mu/ n expect di/9ct vision ( objects ne> ! horizon4 ,objects ne> ! ea/]n horizon dur+ ! "t ( morn+ twilight are especially confus$ by atmosph]ic undulations2 9 fact1 e>ly morn+ is a v unfav\rable "t = ! obs]vation ( all objects4 ,! same rules :i* we h be5 apply+ to refractors1 s]ve = reflectors4 ,! p]=mance ( a reflector w be f\nd to diff] 9 "s respects1 h[ev]1 f t ( a refractor4 ,mr4 ,dawes is1 we believe1 n[ engag$ 9 te/+ reflectors1 & 8 unequall$ exp]i5ce ( refractors w enable him to pron\nce decisively on ! relative m]its ( ! two classes ( telescopes4 ,we h little to say respect+ ! con/ruction ( telescopes4 ,:e!r x is advisable or n = an amateur obs]v] to attempt ! con/ruction ( 8 own telescope is a "q dep5d+ entirely on 8 me*anical ability & +5uity4 ,my own exp]i5ce ( telescope con/ruction is conf9$ to ! conv]sion ( a #c-;feet into a #e-a_/b-;feet telescope4 ,?is op]ation involv$ "s difficulties1 s9ce ! ap]ture _h to be increas$ by ab\t an in*4 ,i f\nd a tub+ made ( alt]nate lay]s ( c>d & calico well pa/$ toge!r1 to be bo? light & /rong4 ,b = ! full l5g? ( tube ,i ?9k a core ( metal is want$4 ,a le>n$ & +5i\s fri5d1 ,mr4 ,%>p1 ,fell[ ( ,/4 ,john's ,college1 in=ms me t a tube ( t91 cov]$ ) lay]s ( br[n pap]1 well pa/$ & ?ick] ne> ! middle ( ! tube1 =ms a light & /rong telescope-tube1 almo/ :olly free f vibration4 ,suff] no inexp]i5c$ p]son to deal ) y\r object-glass4 ,i knew a valuable glass ru9$ by ! proce$+s ( a workman :o _h be5 told to atta* ?ree pieces ( brass r\nd ! cell ( ! d\ble l5s4 ,:at he _h done rema9$ unkn[n1 b ev] aft] a wret*$ gl>e ( light surr\nd$ all objects ( any brilliancy4 ,"o ^w ab\t ! inv]sion ( objects by ! a/ronomical telescope4 ,x is s+ul> t any difficulty %\ld be felt ab\t s simple a matt]1 yet ,i h se5 9 ! writ+s ( m ?an "o di/+ui%$ a/ronom]1 :olly incorrect views z to ! nature ( ! inv]sion4 ,"o tells u t to obta9 ! correct pres5tation f a picture tak5 ) a telescope1 ! view %\ld be inv]t$1 held up to ! light1 & look$ at f ! back ( ! pap]4 ,ano!r tells u to inv]t ! picture & hold x opposite a look+-glass4 ,nei!r me?od is correct4 ,! simple correction want$ is to hold ! picture upside d[n--! same *ange :i* br+s ! top to ! bottom br+s ! "r to ! left1 i4e41 fully corrects ! inv]sion4 ,9 ! case1 h[ev]1 ( a picture tak5 by an ,h]s*elian reflector1 ! inv]sion n be+ complete1 a diff]5t me?od mu/ be adopt$4 ,9 fact1 ei!r ( ! above-nam$ processes1 incorrect = ! ord9>y a/ronomical1 w\ld be correct = ! ,h]s*elian ,telescope4 ,! latt] inv]ts b does n rev]se "r & left2 !re=e aft] inv]t+ our picture we mu/ int]*ange "r & left because !y h be5 rev]s$ by ! inv]sion4 ,?is is effect$ ei!r by look+ at ! picture f beh9d1 or by hold+ x up to a mirror4 ,illu/ration3 ,,plate ,,ii4 ,,*apt] ,,ii4 ,a ,,half-,,h\r ,,) ,,orion1 ,,lepus ,,taurus1 ,,etc4 ,any ( ! half-h\rs "h assign$ to ! con/ellation-seasons may be tak5 fir/1 & ! re/ 9 seasonal or cyclic ord]4 ,! foll[+ introductory rem>ks are applicable to ea*3-- ,if we /& on an op5 space1 on any cle> night1 we see above u ! cele/ial dome spangl$ ) />s1 app>5tly fix$ 9 position4 ,b aft] a little "t x becomes cle> t ^! orbs are sl[ly %ift+ _! position4 ,^? ne> ! ea/]n horizon are ris+1 ^? ne> ! we/]n sett+4 ,c>eful & cont9u\s obs]vation w\ld %[ t ! />s are all mov+ 9 ! same way1 precisely1 z !y w\ld if !y 7 fix$ to ! concave surface ( a va/ holl[ sph]e1 & ?is sph]e rotat$ ab\t an axis4 ,?is axis1 9 our latitude1 is incl9$ ab\t #ea-a_/b to ! horizon4 ,( c\rse only "o end ( ?is imag9>y axis c be above our horizon4 ,?is end lies v ne> a /> :i* x w be well = u to become acqua9t$ ) at ! beg9n+ ( our op]ations4 ,x lies almo/ exactly t[>ds ! nor?1 & is rais$ f #ej to #ec 7accord+ to ! season & h\r7 above ! horizon4 ,!re is an easy me?od ( f9d+ x4 ,we mu/ fir/ f9d ! ,great] ,be>4 ,x w be se5 f ,plate #a1 t on a spr+ ev5+ ! sev5 conspicu\s />s ( ?is con/ellation are to be look$ = t[>ds ! nor?-ea/1 ab\t half way betwe5 ! horizon & ! po9t ov]head 7or z5i?71 ! l5g? ( ! set ( />s be+ v]tical4 ,on a summ]'s ev5+ ! ,great ,be> is ne>ly ov]head4 ,on an autumn ev5+ he is t[>ds ! nor?-we/1 ! l5g? ( ! set ( sev5 be+ some:at incl9$ to ! horizon4 ,f9ally1 on a w9t]'s ev5+1 he is l[ d[n t[>ds ! nor?1 ! l5g? ( ! set ( sev5 />s be+ ne>ly 9 a horizontal direction4 ,hav+ f\nd ! sev5 />s1 we make use ( ! po9t]s alpha & beta 7%[n 9 ,plate #a7 to indicate ! place ( ! ,pole-/>1 ^: di/ance f ! po9t] alpha is r m ?an ?ree times ! di/ance ( alpha f beta4 ,n[ /& fac+ ! ,pole-/>4 ,!n all ! />s are travell+ r\nd t /> 9 a direction contr>y to t 9 :i* ! h&s ( a wat* move4 ,?us ! />s bel[ ! pole are mov+ t[>ds ! "r1 ^? above ! pole t[>ds ! left1 ^? to ! "r ( ! pole upw>ds1 ^? to ! left ( ! pole d[nw>ds4 ,next face ! s\?4 ,!n all ! />s on our left1 t is1 t[>ds ! ea/1 are ris+ slant+ly t[>ds ! s\?2 ^? due s\? are mov+ horizontally to ! "r1 t is1 t[>ds ! we/2 & ^? on our "r are pass+ slant+ly d[nw>ds t[>ds ! we/4 ,x is important to famili>ise ourselves ) ^! motions1 because x is ?r\gh !m t objects pass out ( ! field ( view ( ! telescope1 & by mov+ ! tube 9 a prop] direction we c easily pick up an object t has ?us pass$ away1 :]eas if we are n famili> ) ! v>y+ motions 9 diff]5t p>ts ( ! cele/ial sph]e1 we may fail 9 ! attempt to imm$iately recov] an object1 & wa/e "t 9 ! se>* = x4 ,! consid]ation ( ! cele/ial motions %[s h[ advantage\s x is1 :5 us+ an alt-azimu?1 to obs]ve objects z ne>ly z possible due s\?4 ,( c\rse 9 _m cases ?is is impracticable1 because a ph5om5on we wi% to wat* may occur :5 an object is n situat$ ne> ! m]idian4 ,b 9 exam9+ d\ble />s !re is 9 g5]al no reason = select+ objects inconv5i5tly situat$4 ,we c wait till !y come r\nd to ! m]idian1 & !n obs]ve !m m com=tably4 ,besides1 mo/ objects are high]1 & !re=e bett] se51 :5 due s\?4 ,nor!rn objects1 & especially ^? )9 ! circle ( p]petual app>ition1 (t5 culm9ate 7t is1 cross ! m]idian1 or nor? & s\? l9e7 at too great a height = com=table vision4 ,9 ?is case we %\ld obs]ve !m t[>ds ! ea/ or we/1 & rememb] t 9 ! fir/ case !y are ris+1 & 9 ! latt] !y are sett+1 & t 9 bo? cases !y h also a motion f left to "r4 ,if we all[ an object to pass "r across ! field ( view 7! telescope be+ fix$71 ! app>5t direction ( its motion is ! exact rev]se ( ! true direction ( ! />'s motion4 ,?is w s]ve z a guide 9 %ift+ ! alt-azimu? aft] a /> has pass$ out ( ! field ( view4 ,! foll[+ te*nical t]ms mu/ be expla9$4 ,t "p ( ! field ( view t[>ds :i* ! /> appe>s to move is call$ ! prec$+ "p ( ! field1 ! opposite be+ t]m$ ! foll[+ "p4 ,! motion = all />s1 except ^? ly+ 9 an oval space ext5d+ f ! z5i? to ! pole ( ! heav5s1 is m or less f "r to left 79 ! inv]t$ field74 ,n[1 if we suppose a /> to move along a diamet] ( ! field s z to divide ! field into two semicircles1 !n 9 all cases 9 :i* ?is motion takes places f "r to left1 t semicircle :i* conta9s ! l[e/ po9t 7app>5tly7 ( ! field is ! nor!rn half1 ! o!r is ! s\!rn half4 ,ov] ! oval space j m5tion$ ! rev]se holds4 ,?us ! field is divid$ into f\r quadrants1 & ^! are t]m$ nor? foll[+ 7n4f47 & s\? foll[+ 7s4f472 nor? prec$+ 7n4p471 & s\? prec$+ 7s4p474 ,! /ud5t c h no difficulty 9 int]pret+ ^! t]ms1 s9ce he kn[s :i* is ! foll[+ & :i* ! prec$+ semicircle1 :i* ! nor!rn & :i* ! s\!rn4 ,9 ! figures ( plates #c & #e1 ! lett]s n4f41 n4p41 c41 are affix$ to ! prop] quadrants4 ,x is to be rememb]$ t ! quadrants ?us indicat$ are measur$ ei!r way f ! po9t & fea!r ( ! diametral arr[s4 ,next1 ( ! app>5t annual motion ( ! />s4 ,?is takes place 9 exactly ! same mann] z ! daily motion4 ,if we view ! sky at eight o'clock on any day1 & aga9 at ! same h\r "o mon? lat]1 we %all f9d t at ! latt] obs]vation 7z comp>$ ) ! =m]7 ! heav5s appe> to h rotat$ by ! twelf? "p ( a complete circumf]5ce1 & ! appe>ance pres5t$ is precisely ! same z we %\ld h obs]v$ _h we wait$ = two h\rs 7! twelf? "p ( a day7 on ! day ( ! fir/ obs]vation4 99 99 99 99 99 ,our survey ( ! heav5s is suppos$ to be comm5c$ dur+ ! fir/ qu>t] ( ! ye>1 at t5 o'clock on ! #bj? ( ,janu>y1 or at n9e on ! #e? ( ,febru>y1 or at eight on ! #ai? ( ,febru>y1 or at sev5 on ! #f? ( ,m>*1 or at h\rs int]m$iate to ^! on int]m$iate days4 ,we look fir/ = ! ,great ,be> t[>ds ! nor?-ea/1 z already describ$1 & !nce f9d ! ,pole-/>2 turn+ t[>ds :i* we see1 t[>ds ! "r & d[nw>ds1 ! two gu>dians ( ! pole 7beta & gamma ,urs ,m9oris74 ,imm$iately "u ! ,pole-/> is ! ,dragon's ,head1 a conspicu\s diamond ( />s4 ,j on ! horizon is ,vega1 sc9tillat+ brilliantly4 ,ov]head is ! brilliant ,capella1 ne> :i* ! ,milky ,way is se5 pass+ d[n to ! horizon on ei!r side t[>ds ! qu>t]s ,s4,s4,e4 & ,n4,n4,w4 ,= ! pres5t our bus9ess is ) ! s\!rn heav5s1 h[ev]4 ,fac+ ! s\?1 we see a brilliant array ( />s1 ,sirius unmi/akeably ov]%9+ ! re/4 ,orion is %9+ 9 full glory1 8 lead+ brilliant1 ,betelgeuse#b be+ almo/ exactly on ! m]idian1 & also almo/ exactly half way betwe5 ! horizon & ! z5i?4 ,9 ,plate #b is giv5 a map ( ?is con/ellation & its neighb\rhood4 ,let u fir/ turn ! tube on ,sirius4 ,x is easy to get him 9 ! field )\t ! aid ( a f9d]4 ,! se>* w s]ve to illu/rate a me?od (t5 useful :5 a telescope has no f9d]4 ,hav+ tak+ out ! eye-piece--a l[-p[] "o1 suppose--direct ! tube ne>ly t[>ds ,sirius4 ,on look+ ?r\gh x1 a gl>e ( light w be se5 )9 ! tube4 ,n[1 if ! tube be slightly mov$ ab\t1 ! light w be se5 to wax & wane1 accord+ z ! tube is m or less accurately direct$4 ,foll[+ ^! indications1 x w be f\nd easy to direct ! tube1 s t ! object-glass %all appe> full ( light4 ,:5 ?is is done1 ins]t ! eye-piece1 & ! /> w be se5 9 ! field4 ,b ! telescope is out ( focus1 !re=e we mu/ turn ! small focuss+ screw4 ,obs]ve ! *>m+ *romatic *anges--gre51 & r$1 & blue light1 pur] ?an ! hues ( ! ra9b[1 sc9tillat+ & coruscat+ ) wond]ful brilliancy4 ,z we get ! focus1 ! excursions ( ^! light fla%es dim9i% until--if ! wea!r is fav\rable--! /> is se51 /ill sc9tillat+1 & mu* bright] ?an to ! nak$ eye1 b r$uc$ to a small disc ( light1 surr\nd$ 79 ! case ( s bright a /> z ,sirius7 ) a slight gl>e4 ,if aft] obta9+ ! focus ! focuss+ rack "w be /ill turn$1 we see a coruscat+ image z be=e4 ,9 ! case ( a v brilliant /> ^! coruscations are s *>m+ t we may be excus$ = call+ ! obs]v]'s att5tion to !m4 ,! subject is n )\t int]e/ & difficulty z an optical "o4 ,b ! a/ronom]'s object is to get rid ( all ^! flames & sprays ( col\r$ light1 s t he has v little sympa?y ) ! admiration :i* ,wordswor? is said to h express$ = out-(-focus views ( ! />s4 ,we pass to m legitimate obs]vations1 notic+ 9 pass+ t ,sirius is a d\ble />1 ! companion be+ ( ! t5? magnitude1 & di/ant ab\t t5 seconds f ! prim>y4 ,b our beg9n] is n likely to see ! companion1 :i* is a v difficult object1 v[+ to ! ov]p[]+ brilliancy ( ! prim>y4 ,orion af=ds ! obs]v] a spl5did field ( rese>*4 ,x is a con/ellation ri* 9 d\ble & multiple />s1 clu/]s1 & nebul4 ,we w beg9 ) an easy object4 ,! /> delta 7,plate #c71 or ,m9taka1 ! upp]mo/ ( ! ?ree />s =m+ ! belt1 is a wide d\ble4 ,! prim>y is ( ! second magnitude1 ! second>y ( ! sev5?1 bo? be+ :ite4 ,! /> alpha 7,betelgeuse7 is an int]e/+ object1 on acc\nt ( its col\r & brilliance1 & z "o ( ! mo/ rem>kable v>iables 9 ! heav5s4 ,x 0 fir/ obs]v$ to be v>iable by ,sir ,john ,h]s*el 9 #ahcf4 ,at ?is p]iod its v>iations 7 mo/ m>k$ & /rik+4 ,?is cont9u$ until #ahdj1 :5 ! *anges became mu* less conspicu\s4 ,9 ,janu>y1 #ahdi1 !y _h recomm5c$1 & on ,decemb] #e?1 #aheb1 ,mr4 ,flet*] obs]v$ alpha ,orionis bright] ?an ,capella1 & actually ! l>ge/ /> 9 ! nor!rn hemisph]e4 ,t a /> s conspicu\s1 & presumably s l>ge1 %\ld pres5t su* rem>kable v>iations1 is a circum/ance :i* adds an additional int]e/ to ! results :i* h rew>d$ ! spectrum-analysis ( ?is /> by ,mr4 ,hugg9s & ,pr(essor ,mill]4 ,x appe>s t !re is decisive evid5ce ( ! pres5ce 9 ?is lum9>y ( _m elem5ts kn[n to exi/ 9 our own sun2 among/ o!rs are f\nd sodium1 magnesium1 calcium1 iron1 & bismu?4 ,hydrog5 appe>s to be abs5t1 or1 m correctly1 !re are no l9es 9 ! />'s spectrum correspond+ to ^? ( hydrog5 9 ! sol> spectrum4 ,sec*i consid]s t !re is evid5ce ( an actual *ange 9 ! spectrum ( ! />1 an op9ion 9 :i* ,mr4 ,hugg9s does n co9cide4 ,9 ! telescope ,betelgeuse appe>s z a ri* & brilliant gem1 says ,lassell1 a ri* topaz1 9 hue & brilliancy diff]+ f any t ,i h se54 ,turn next to beta 7,rigel71 ! brighte/ /> bel[ ! belt4 ,?is is a v not$ d\ble1 & w sev]ely te/ our obs]v]'s telescope1 if small4 ,! compon5ts are well sep>at$ 7see ,plate #c71 comp>$ ) _m easi] d\bles2 ! second>y is also ( ! sev5? magnitude1 s t nei!r z respects clos5ess nor smallness ( ! second>y1 is ,rigel a difficult object4 ,x is ! comb9ation ( ! two features :i* makes x a te/-object4 ,kit*5] says a #a-c_/d-;in* object-glass %\ld %[ ,rigel d\ble2 9 e>li] editions ( 8 "w he gave #b-c_/d-;in*es z ! necess>y ap]ture4 ,smy? m5tions ,rigel z a te/ = a #d-;in* ap]ture1 ) p[]s ( f #hj to #abj4 ,a #c-;in* ap]ture1 h[ev]1 w c]ta9ly %[ ! companion4 ,rigel is an orange />1 ! companion blue4 ,turn next to lambda ! nor!rnmo/ ( ! set ( ?ree />s 9 ! head ( ,orion4 ,?is is a triple />1 ?\gh an ap]ture ( #c in*es w %[ x only z a d\ble4 ,! compon5ts are #e ap>t1 ! col\rs pale :ite & violet4 ,) ! full p[]s ( a #c-a_/b-;in* glass a fa9t companion may be se5 above lambda4 ,! /> zeta1 ! l[e/ 9 ! belt1 may be tri$ ) a #c-a_/b-;in* glass4 ,x is a close d\ble1 ! compon5ts be+ ne>ly equal1 & ab\t #b-a_/b ap>t 7see ,plate #c74 ,= a *ange we w n[ try our telescope on a nebula1 select+ ! great nebula 9 ! ,sword4 ,! place ( ?is object is indicat$ 9 ,plate #b4 ,!re c be no difficulty 9 f9d+ x s9ce x is cle>ly visible to ! nak$ eye on a moonless night--! only sort ( night on :i* an obs]v] w\ld c>e to look at nebul4 ,a l[ p[] %\ld be employ$4 ,! nebula is %[n 9 ,plate #c z ,i h se5 x ) a #c-;in* ap]ture4 ,we see no?+ ( ^? complex /reams ( light :i* are portray$ 9 ! draw+s ( ,h]s*el1 ,bond1 & ,lassell1 b en\gh to excite our int]e/ & wond]4 ,:at is ?is m>vell\s light-cl\d8 ,"o c\ld almo/ imag9e t !re 0 a /range prophetic mean+ 9 ! words :i* h be5 translat$ ,can/ ?\ loose ! b&s ( ,orion8 ,telescope aft] telescope _h be5 turn$ on ?is wond]ful object ) ! hope ( resolv+ its light into />s4 ,b x prov$ intractable to ,h]s*el's great reflector1 to ,lassell's #b-;feet reflector1 to ,"l ,rosse's #c-;feet reflector1 & ev5 p>tially to ! great #f-;feet reflector4 ,!n we he> ( its suppos$ resolution into />s1 ,"l ,rosse himself writ+ to ,pr(essor ,ni*ol1 9 #ahdf1 ,i may safely say !re c be little1 if any1 d\bt z to ! resolvability ( ! nebula2--all ab\t ! trapezium is a mass ( />s1 ! re/ ( ! nebula also ab\nd+ ) />s1 & exhibit+ ! *>act]i/ics ( resolvability /rongly m>k$4 ,x 0 decid$1 !re=e1 t assur$ly ! great nebula is a cong]ies ( />s1 & n a mass ( nebul\s matt] z _h be5 surmis$ by ,sir ,w4 ,h]s*el4 ,& !re=e a/ronom]s 7 n a little surpris$ :5 x 0 prov$ by ,mr4 ,hugg9s' spectrum-analysis t ! nebula consi/s ( gase\s matt]4 ,h[ widely ext5d$ ?is gase\s univ]se may be we _c say4 ,! g5]al op9ion is t ! nebul are remov$ f> beyond ! fix$ />s4 ,if ?is 7 s1 ! dim5sions ( ! ,orion nebula w\ld be inde$ enorm\s1 f> l>g] probably ?an ^? ( ! :ole sy/em :]e( our sun is a memb]4 ,i believe ?is view is f\nd$ on insuffici5t evid5ce1 b ?is w\ld n be ! place to discuss ! subject4 ,i %all m]ely po9t out t ! nebula occurs 9 a region ri* 9 />s1 & if x is n1 l ! great nebula 9 ,argo1 clu/]$ ar\nd a rem>kable />1 x is f\nd associat$ 9 a mann] :i* ,i _c look ^u z accid5tal ) a set ( small-magnitude />s1 & notably ) ! trapezium :i* surr\nds t v rem>kable black gap )9 ! nebula4 ,! fact t ! nebula %>es ! prop] motion ( ! trapezium appe>s inexplicable if ! nebula is really f> out 9 space beyond ! trapezium4 ,a v small prop] motion ( ! trapezium 7alone7 w\ld long s9ce h de/roy$ ! rem>kable agreem5t 9 ! position ( ! d>k gap & ! trapezium :i* has be5 notic$ = s _m ye>s4 ,b :e!r belong+ to our sy/em or f> beyond x1 ! great nebula mu/ h enorm\s dim5sions4 ,a va/ gase\s sy/em x is1 su/a9$ by :at arrangem5ts or =ces we _c tell1 nor c we "k :at purposes x subs]ves4 ,mr4 ,hugg9s' discov]y t comets h gase\s nuclei1 7s f> z ! two he has yet exam9$ %[7 may sugge/ ! speculation t 9 ! ,orion nebula we see a va/ sy/em ( comets travell+ 9 ext5sive orbits ar\nd nucle> />s1 & s sl[ly z to exhibit = long int]vals ( "t an un*ang$ figure4 ,b ( su* speculations we may say ) ,sir ,j4 ,h]s*el !re is no end4 ,to return to our telescopic obs]vations3--,! trapezium af=ds a useful te/ = ! light-ga!r+ p[] ( ! telescope4 ,l>ge in/rum5ts exhibit n9e />s4 ,b our obs]v] may be well satisfi$ ) 8 in/rum5t & 8 eye-sight if he c see five ) a #c-a_/b-;in* ap]ture4#c ,a good #c-;in* glass %[s f\r di/9ctly4 ,b ) small] ap]tures only ?ree are visible4 ,! :ole neighb\rhood ( ! great nebula w well repay rese>*4 ,! obs]v] may sweep ov] x c>efully on any d>k night ) pr(it4 ,above ! nebula is ! />-clu/] #cfb ,h4 ,! /> iota 7d\ble z %[n 9 ,plate #c7 bel[ ! nebula is involv$ 9 a /rong nebulosity4 ,& 9 se>*+ ov] ?is region we meet ) delicate d\ble1 triple1 & multiple />s1 :i* make ! survey int]e/+ ) almo/ any p[] t may be appli$4 ,above ! nebula is ! /> sigma1 a multiple />4 ,to an obs]v] ) a good #c-a_/b-;in* glass sigma appe>s z an octuple />4 ,x is well se51 h[ev]1 z a f9e multiple /> ) a small] ap]ture4 ,"s ( ! />s ( ?is gr\p appe> to be v>iable4 ,! /> rho ,orionis is an unequal1 easy d\ble1 ! compon5ts be+ sep>at$ by ne>ly sev5 seconds4 ,! prim>y is orange1 ! small] /> smalt-blue 7see ,plate #c74 ,! middle /> ( ! belt 7epsilon7 has a di/ant blue companion4 ,?is />1 l iota1 is nebul\s4 ,9 fact1 ! :ole region )9 ! triangle =m$ by />s gamma1 kappa & beta is full ( nebul\s d\ble & multiple />s1 ^: aggregation 9 ?is region ,i d n consid] :olly accid5tal4 ,we h n explor$ half ! weal? ( ,orion1 b leave mu* = future obs]vation4 ,we mu/ turn1 h[ev]1 to o!r con/ellations4 ,bel[ ,orion is ,lepus1 ! ,h>e1 a small con/ellation conta9+ "s rem>kable d\bles4 ,among ^! we may note xi1 a :ite /> ) a sc>let companion2 gamma1 a yell[ & g>net d\ble2 & iota1 a d\ble />1 :ite & pale violet1 ) a di/ant r$ companion4 ,! /> kappa ,leporis is a r close d\ble1 :ite ) a small gre5 companion4 ,! int5sely r$ /> ,r ,leporis 7a v>iable7 w be f\nd 9 ! position indicat$ 9 ! map4 ,/ill keep+ )9 ! b\nd>y ( our map1 we may next turn to ! f9e clu/] #b ,h 7vii47 9 ,monoc]os4 ,?is clu/] is visible to ! nak$ eye1 & w be easily f\nd4 ,! nebula #b ,h 7iv47 is a rem>kable "o ) a p[]ful telescope4 ,! /> #aa ,monoc]otis is a f9e triple /> describ$ by ! eld] ,h]s*el z "o ( ! f9e/ sights 9 ! heav5s4 ,our obs]v]1 h[ev]1 w see x z a d\ble 7see ,plate #c74 delta ,monoc]otis is an easy d\ble1 yell[ & lav5d]4 ,we may n[ leave ! region cov]$ by ! map & take a survey ( ! heav5s = "s objects well se5 at ?is season4 ,t[>ds ! s\?-ea/1 high up above ! horizon1 we see ! tw9-/>s ,ca/or & ,pollux4 ,! upp] is ,ca/or1 ! f9e/ d\ble /> visible 9 ! nor!rn heav5s4 ,! compon5ts are ne>ly equal & r m ?an #e ap>t 7see ,plate #c74 ,bo? are :ite accord+ to ! be/ obs]v]s1 b ! small] is ?\ght by "s to be slightly gre5i%4 ,pollux is a co>se b f9e triple /> 79 l>ge in/rum5ts multiple74 ,! compon5ts orange1 grey1 & lilac4 ,!re are _m o!r f9e objects 9 ,gem9i1 b we pass to ,canc]4 ,! f9e clu/] ,prsepe 9 ,canc] may easily be f\nd z x is di/9ctly visible to ! nak$ eye 9 ! position %[n 9 ,plate #a1 ,map ,i4 ,9 ! telescope x is se5 z %[n 9 ,plate #c4 ,! /> iota ,cancri is a wide d\ble1 ! col\rs orange & blue4 ,procyon1 ! fir/-magnitude /> betwe5 ,prsepe & ,sirius1 is f9ely col\r$--yell[ ) a di/ant orange companion1 :i* appe>s to be v>iable4 ,bel[ ! ,tw9s1 almo/ 9 a l9e ) !m1 is ! /> alpha ,hydr1 call$ ,al ,f>d1 or ! ,solit>y ,"o4 ,x is a #bnd magnitude v>iable4 ,i m5tion x1 h[ev]1 n on its own acc\nt1 b z a guide to ! f9e d\ble epsilon ,hydr4 ,?is /> is ! middle "o ( a gr\p ( ?ree1 ly+ betwe5 ,pollux & ,al ,f>d r ne>] ! latt]4 ,! compon5ts ( epsilon ,hydr are sep>at$ by ab\t #c-a_/b 7see ,plate #c74 ,! prim>y is ( ! f\r?1 ! companion ( ! eigh? magnitude2 ! =m] is yell[1 ! latt] a ruddy purple4 ,! p]iod ( epsilon ,hydr is ab\t #dej ye>s4 ,! con/ellation ,leo ,m9or1 n[ due ea/ & ab\t midway betwe5 ! horizon & ! z5i?1 is well wor? sweep+ ov]4 ,x conta9s sev]al f9e fields4 ,let u next turn to ! we/]n heav5s4 ,"h !re are "s notewor?y objects4 ,to beg9 )1 !re are ! ,pleiades1 %[+ to ! nak$ eye only six or sev5 />s4 ,9 ! telescope ! ,pleiades appe> z %[n 9 ,plate #c4 ,! ,hyades also %[ "s f9e fields ) l[ p[]s4 ,aldeb>an1 ! pr9cipal /> ( ! ,hyades1 z also ( ! con/ellation ,taurus1 is a not$ r$ />4 ,x is *iefly rem>kable = ! close spectroscopic analysis to :i* x has be5 subject$ by ,messrs4 ,hugg9s & ,mill]4 ,unlike ,betelgeuse1 ! spectrum ( ,aldeb>an exhibits ! l9es correspond+ to hydrog51 & no less ?an eight metals--sodium1 magnesium1 calcium1 iron1 bismu?1 tellurium1 antimony1 & m]cury1 are prov$ to exi/ 9 ! con/itution ( ?is brilliant r$ />4 ,on ! "r ( ,aldeb>an1 9 ! position indicat$ 9 ,plate #a1 ,map ,i41 are ! />s zeta & beta ,tauri4 ,if ) a l[ p[] ! obs]v] sweep f zeta t[>ds beta1 he w soon f9d--n f> f zeta 7at a di/ance ( ab\t "o-six? ( ! di/ance sep>at+ beta f zeta71 ! celebrat$ ,crab nebula1 kn[n z #a ,m4 ,?is 0 ! fir/ nebula discov]$ by ,messi]1 & its discov]y l$ to ! =mation ( 8 catalogue ( #ajc nebul4 ,9 a small telescope ?is object appe>s z a nebul\s light ( oval =m1 no traces be+ se5 ( ! wisps & sprays ( light pres5t$ 9 ,"l ,rosse's well kn[n picture ( ! nebula4 ,"h ,i %all conclude ! lab\rs ( our fir/ half-h\r among ! />s1 notic+ t ! exam9ation ( ,plate #a w %[ :at o!r con/ellations besides ^? "h consid]$ are well situat$ = obs]vation at ?is season4 ,x w be rem>k$ t _m con/ellations well se5 9 ! ?ird half-h\r 7,*apt] ,,iv47 are fav\rably se5 9 ! fir/ also1 & vice v]s4 ,= in/ance1 ! con/ellation ,ursa ,major well-plac$ t[>ds ! nor?-ea/ 9 ! fir/ qu>t] ( ! ye>1 is equally well-plac$ t[>ds ! nor?-we/ 9 ! ?ird1 & simil>ly ( ! con/ellation ,cassiopeia4 ,! same relation connects ! second & f\r? qu>t]s ( ! ye>4 ,illu/ration3 ,,plate ,,iii4 ,,*apt] ,,iii4 ,a ,,half-,,h\r ,,) ,,lyra1 ,,h]cules1 ,,corvus1 ,,crat]1 ,,etc4 ,! obs]vations n[ to be comm5c$ are suppos$ to take place dur+ ! second qu>t] ( ! ye>1--at t5 o'clock on ! #bj? ( ,april1 or at n9e on ! #e? ( ,may1 or at eight on ! #ba/ ( ,may1 or at sev5 on ! #e? ( ,june1 or at h\rs int]m$iate to ^! on int]m$iate days4 ,we aga9 look fir/ = ! ,great ,be>1 n[ ne> ! z5i?1 & !nce f9d ! ,pole-/>4 ,turn+ t[>ds ! nor?1 we see ,cassiopeia betwe5 ! ,pole-/> & ! horizon4 ,t[>ds ! nor?-we/ is ! brilliant ,capella1 & t[>ds ! nor?-ea/ ! equally brilliant ,vega1 b5ea? :i*1 & some:at nor!rly1 is ! cross 9 ,cygnus4 ,! ,milky ,way passes f ! ea/]n horizon t[>ds ! nor? 7l[ d[n71 & s r\nd to ! we/]n horizon4 ,9 select+ a region = special obs]vation1 we %all adopt a diff]5t plan f t us$ 9 ! prec$+ half-h\r4 ,! region on ! equator & t[>ds ! s\? is inde$ p>ticul>ly int]e/+1 s9ce x includes ! nebul> region 9 ,virgo4 ,)9 ?is space nebul are clu/]$ m closely ?an ov] any correspond+ space 9 ! heav5s1 save only ! great] ,magellanic cl\d4 ,b to ! obs]v] ) telescopes ( mod]ate p[] ^! nebul pres5t few features ( special int]e/2 & !re are regions ( ! sky n[ well situat$ = obs]vation1 :i*1 at mo/ o!r epo*s are ei!r l[ d[n t[>ds ! horizon or inconv5i5tly ne> to ! z5i?4 ,we %all !re=e select "o ( ^!1 ! region includ$ 9 ! second map ( ,plate #b1 & ! neighb\r+ "p ( ! cele/ial sph]e4 ,at any ( ! h\rs above nam$1 ! con/ellation ,h]cules lies t[>ds ! ea/4 ,a quadrant tak5 f ! z5i? to ! ea/]n horizon passes close to ! la/ /> 7eta7 ( ! ,great ,be>'s tail1 ?r\gh beta1 a /> 9 ,bootes' head1 ne> beta ,h]culis1 betwe5 ! two ,alphas :i* m>k ! heads ( ,h]cules & ,ophiu*us1 & s pa/ beta ,ophiu*i1 a ?ird-magnitude /> ne> ! horizon4 ,& "h we may turn aside = a mom5t to notice ! rem>kable v]tical r[ ( six conspicu\s />s t[>ds ! ea/-s\?-ea/2 ^! are1 c\nt+ !m 9 ord] f ! horizon1 zeta1 epsilon1 & delta ,ophiu*i1 epsilon1 alpha1 & delta ,s]p5tis4 ,let ! telescope fir/ be direct$ t[>ds ,vega4 ,?is orb pres5ts a brilliant appe>ance 9 ! telescope4 ,its col\r is a blui%-:ite4 ,9 an ord9>y telescope ,vega appe>s z a s+le />1 b ) a l>ge object-glass two di/ant small companions are se54 ,a n9e-in* glass %[s also two small companions )9 a few seconds ( ,vega4 ,9 ! great ,h>v>d refractor ,vega is se5 ) no less ?an ?irty-five companions4 ,i imag9e t all ^! />s1 & o!rs :i* c be se5 9 neighb\r+ fields1 indicate ! association ( ,vega ) ! neighb\r+ /ream ( ! ,milky ,way4 ,let our obs]v] n[ direct 8 telescope to ! /> epsilon ,lyr4 ,or r1 let him fir/ closely exam9e ?is /> ) ! nak$ eye4 ,! /> is easily id5tifi$1 s9ce x lies to ! left ( ,vega1 =m+ ) zeta a small equilat]al triangle4 ,a c>eful scrut9y suffices to indicate a peculi>ity 9 ?is />4 ,if our obs]v] possesses v good eye-sight1 he w di/9ctly recognise x z a nak$-eye d\ble2 b m probably he w only notice t x appe>s l5g!n$ 9 a nor? & s\? direction4#d ,9 ! f9d] ! /> is easily divid$4 ,apply+ a l[ p[] to ! telescope itself1 we see epsilon ,lyr z a wide d\ble1 ! l9e jo9+ ! compon5ts ly+ ne>ly nor? & s\?4 ,! s\!rnmo/ compon5t 7! upp] 9 ! figure7 is call$ epsilon#a1 ! o!r epsilon#b4 ,se5 z a d\ble1 bo? compon5ts appe> :ite4 ,n[1 if ! obs]v]'s telescope is suffici5tly p[]ful1 ea* ( ! compon5ts may be se5 to be itself d\ble4 ,fir/ try epsilon#a1 ! nor!rn pair4 ,! l9e jo9+ ! compon5ts is direct$ z %[n 9 ,plate #c4 ,! di/ance betwe5 !m is #cb1 _! magnitudes #e & #f-a_/b1 & _! col\rs yell[ & ruddy4 ,if ! obs]v] succe$s 9 see+ epsilon#a fairly divid$1 he w probably n fail 9 detect+ ! duplicity ( epsilon#b1 ?\gh ?is is a r clos] pair1 ! di/ance betwe5 ! compon5ts be+ only #bf4 ,! magnitudes are #e & #e-a_/b1 bo? be+ :ite4 ,betwe5 epsilon#a & epsilon#b are ?ree fa9t />s1 possibly =m+ ) ! quadruple a s+le sy/em4 ,let u next turn to ! ?ird /> ( ! equilat]al triangle m5tion$ above--viz4 to ! /> zeta ,lyr4 ,?is is a spl5did b easy d\ble4 ,x is figur$ 9 ,plate #c1 b x mu/ be notic$ t ! figure ( zeta & ! o!r n9e small figures are n drawn on ! same scale z epsilon ,lyr4 ,! actual di/ance betwe5 ! compon5ts ( zeta ,lyra is #dd1 or ab\t "o-f\r? ( ! di/ance sep>at+ epsilon#a f epsilon#b4 ,! compon5ts ( zeta are v ne>ly equal 9 magnitude1 9 col\r topaz & gre51 ! topaz compon5t be+ e/imat$ z ( ! fif? magnitude1 ! gre5 compon5t int]m$iate betwe5 ! fif? & six? magnitudes4 ,we may n[ turn to a /> n figur$ 9 ! map1 b readily f\nd4 ,x w be notic$ t ! />s epsilon1 alpha1 beta1 & gamma =m1 ) two small />s t[>ds ! left1 a some:at regul> hexagonal figure--a hexagon1 9 fact1 hav+ ?ree equal long sides & ?ree ne>ly equal %ort sides alt]nat+ ) ! o!rs4 ,! /> eta ,lyr =ms ! angle next to epsilon4 ,x is a wide & unequal d\ble1 z figur$ 9 ,plate #c4 ,! l>g] compon5t is azure blue2 ! small] is violet1 &1 be+ only ( ! n9? magnitude1 is some:at difficult to cat* ) ap]tures "u #c in*es4 ,! /> delta#b ,lyr is orange1 delta#a blue4 ,9 ! same field ) ^! are se5 _m o!r />s4 ,! />s gamma#a & gamma#b may also be se5 9 a s+le field1 ! di/ance betwe5 !m be+ ab\t half ! moon's mean diamet]4 ,! =m] is quadruple1 ! compon5ts be+ yell[1 blui%1 pale blue1 & blue4 ,turn next to ! />s beta & gamma ,lyr1 ! =m] a multiple1 ! latt] an unequal d\ble />4 ,x is n1 h[ev]1 9 ^! respects t ^! />s are *iefly int]e/+1 b = _! v>iability4 ,! v>iability ( gamma has n inde$ be5 fully e/abli%$1 ?\gh x is c]ta9 t1 hav+ once be5 less bright1 gamma is n[ consid]ably bright] ?an beta4 ,! *ange1 h[ev]1 may be due to ! v>iation ( beta alone4 ,?is /> is "o ( ! mo/ rem>kable v>iables kn[n4 ,its p]iod is #ab;d4 #ba;h4 #ecm4 #ajs4 ,9 ?is "t x passes f a maximum brilliancy--t ( a /> ( ! #cd magnitude--to a m9imum lu/re equal to t ( a /> ( ! #dc magnitude1 !nce to ! same maximum brilliancy z be=e1 !nce to ano!r m9imum ( lu/re--t ( a /> ( ! #de magnitude--& s to its maximum lu/re aga91 :5 ! cycle ( *anges recomm5ces4 ,^! rem>kable *anges seem to po9t to ! exi/5ce ( two unequal d>k satellites1 ^: dim5sions be> a mu* great] proportion to ^? ( ! bright compon5ts ( beta ,lyr ?an ! dim5sions ( ! memb]s ( ! ,sol> ,sy/em be> to ^? ( ! sun4 ,9 ?is case1 at any rate1 ! conjecture haz>d$ ab\t ,algol1 t ! /> revolves ar\nd a d>k c5tral orb1 w\ld be insuffici5t to acc\nt = ! obs]v$ v>iation4 ,ne>ly midway betwe5 beta & gamma lies ! wond]ful r+-nebula #eg ,m1 ( :i* an imp]fect idea w be convey$ by ! la/ figure ( ,plate #c4 ,?is nebula 0 discov]$ 9 #aggb1 by ,d>qui]1 at ,t\l\se4 ,x is se5 z a r+ ( light ) v mod]ate telescopic p[]4 ,9 a good #c-a_/b-;in* telescope ! nebula exhibits a mottl$ appe>ance & a sp>kl+ light4 ,l>g] in/rum5ts exhibit a fa9t light )9 ! r+2 & 9 ,"l ,rosse's great ,telescope wisps ( />s are se5 )91 & fa9t /reaks ( light /ream f ! out] bord] ( ! r+4 ,?is nebula has be5 subject$ to spectrum-analysis by ,mr4 ,hugg9s4 ,x turns out to be a gase\s nebula6 ,9 fact1 r+-nebul--( :i* only sev5 h be5 detect$--seem to belong to ! same class z ! planet>y nebul1 all ( :i* exhibit ! l9e-spectrum indicative ( gaseity4 ,! brighte/ ( ! ?ree l9es se5 9 ! spectrum ( ! r+-nebula 9 ,lyra pres5ts a r peculi> appe>ance1 s9ce x consi/s1 says ,mr4 ,hugg9s1 ( two bright dots1 correspond+ to sections ( ! r+1 & betwe5 ^! !re is n d>kness1 b an excessively fa9t l9e jo9+ !m4 ,?is obs]vation makes x probable t ! fa9t nebul\s matt] occupy+ ! c5tral portion is simil> 9 con/itution to t ( ! r+4 ,! con/ellation ,h]cules also conta9s _m v int]e/+ objects4 ,let u fir/ inspect a nebula pres5t+ a rem>kable contra/ ) t j describ$4 ,i ref] to ! nebula #ac ,m1 kn[n z ,halley's nebula 7,plate #c74 ,?is nebula is visible to ! nak$ eye1 & 9 a good telescope x is a mo/ wond]ful object3 p]haps no "o ev] saw x = ! fir/ "t )\t utt]+ a %\t ( wond]4 ,x requires a v p[]ful telescope completely to resolve ?is f9e nebula1 b ! outly+ /ream]s may be resolv$ ) a good #c-;in* telescope4 ,sir ,w4 ,h]s*el consid]$ t ! numb] ( ! />s compos+ ?is wond]ful object 0 at lea/ #ad1jjj4 ,! accept$ views respect+ nebul w\ld place ?is & o!r clu/]s f> beyond ! limits ( our sid]eal sy/em1 & w\ld make ! compon5t />s n v unequal 7on ! av]age7 to our own sun4 ,x seems to me f> m probable1 on ! contr>y1 t ! clu/] belongs to our own sy/em1 & t its compon5ts are v mu* small] ?an ! av]age ( sep>ate />s4 ,p]haps ! :ole mass ( ! clu/] does n exce$ t ( an av]age fir/-magnitude />4 ,! nebul #ib ,m & #ej ,h may be f\nd1 aft] a little se>*+1 f ! positions indicat$ 9 ! map4 ,!y are bo? well wor?y ( /udy1 ! =m] be+ a v bright globul> clu/]1 ! latt] a bright & l>ge r\nd nebula4 ,! spectra ( ^!1 z ( ! great clu/]1 resemble ! sol> spectrum1 be+ cont9u\s1 ?\gh1 ( c\rse1 v mu* fa9t]4 ,! /> delta ,h]culis 7se5 at ! bottom ( ! map7 is a wide & easy d\ble--a beautiful object4 ,! compon5ts1 situat$ z %[n 9 ,plate #c1 are ( ! f\r? & eigh? magnitude1 & col\r$ respectively gre5i%-:ite & grape-r$4 ,! /> kappa ,h]culis is n %[n 9 ! map1 b may be v readily f\nd1 ly+ betwe5 ! two gammas1 gamma ,h]culis & gamma ,s]p5tis 7see ,frontispiece1 ,map #b71 r ne>] ! latt]4 ,x is a wide d\ble1 ! compon5ts ( fif? & sev5? magnitude1 ! l>g] yell[i%-:ite1 ! small] ruddy yell[4#e ,ras ,alge?i1 or alpha ,h]culis1 is also beyond ! limits ( ! map1 b may be easily f\nd by means ( ,map #b1 ,frontispiece4 ,x is1 prop]ly speak+1 a multiple />4 ,consid]$ z a d\ble1 ! arrangem5t ( ! compon5ts is t %[n 9 ,plate #c4 ,! l>g] is ( magnitude #c-a_/b1 ! small] ( magnitude #e-a_/b2 ! =m] orange1 ! latt] em]ald4 ,! companion />s are small1 & require a good telescope to be well se54 ,ras ,alge?i is a v>iable1 *ang+ f magnitude #c to magnitude #c-a_/b 9 a p]iod ( #ff-a_/c days4 ,! /> rho ,h]culis is a clos] d\ble4 ,! compon5ts are #cg ap>t1 & situat$ z %[n 9 ,plate #c4 ,! l>g] is ( magnitude #d1 ! small] #e-a_/b2 ! =m] blui%-:ite1 ! latt] pale em]ald4 ,!re are o!r objects )9 ! range ( our map :i* are well wor?y ( /udy4 ,su* are mu ,draconis1 a beautiful m9iature ( ,ca/or2 gamma#a & gamma#b ,draconis1 a wide d\ble1 ! di/ance betwe5 ! compon5ts be+ ne>ly #fb 7bo? grey72 & gamma#a & gamma#b ,coron1 a nak$-eye d\ble1 ! compon5ts be+ #f' ap>t1 & ea* d\ble ) a good #c-;in* telescope4 ,we turn1 h[ev]1 to ano!r region ( ! sky4 ,l[ d[n1 t[>ds ! s\? is se5 ! small con/ellation ,corvus1 recognis$ by its irregul> quadrilat]al ( />s4 ,( ! two upp] />s1 ! left-h& "o is ,algorab1 a wide d\ble1 ! compon5ts plac$ z 9 ,plate #c1 #bce ap>t1 ! l>g] ( magnitude #c1 ! small] #h-a_/b1 ! col\rs pale yell[ & purple4 ,!re is a r$ /> 9 ?is neighb\rhood :i* is well wor? look+ =4 ,to ! "r ( ,corvus is ! con/ellation ,crat]1 easily recognis$ z =m+ a tol]ably well-m>k$ small gr\p4 ,! /> ,alkes1 or alpha ,crat]is1 mu/ fir/ be f\nd4 ,x is f> f be+ ! brighte/ /> 9 ! con/ellation1 & may be assum$ to h dim9i%$ consid]ably 9 brilliancy s9ce x 0 entitl$ alpha by ,bay]4 ,x w easily be f\nd1 h[ev]1 by means ( ! obs]v]'s /> maps4 ,if n[ ! telescope be direct$ to ,alkes1 !re w be f\nd1 foll[+ him at a di/ance ( #dbe s1 & ab\t "o m9ute s\!rly1 a small r$ />1 ,r4 ,crat]is4 ,l mo/ r$ />s1 ?is "o is a v>iable4 ,a some:at small] blue /> may be se5 9 ! same field4 ,!re is ano!r r$ /> :i* may be f\nd pretty easily at ?is season4 ,fir/ f9d ! />s eta & omicron ,leonis1 ! =m] =m+ ) ,regulus 7n[ ly+ t[>ds ! s\?-we/1 & almo/ exactly midway betwe5 ! z5i? & ! horizon7 ! h&le ( ! ,sickle 9 ,leo1 ! o!r f>!r (f f ,regulus t[>ds ! "r1 b l[] d[n4 ,n[ sweep f omicron t[>ds eta ) a l[ p[]4#f ,!re w be f\nd a six?-magnitude /> ab\t "o-f\r? ( ! way f omicron to eta4 ,s\?1 foll[+ ?is1 w be f\nd a gr\p ( f\r />s1 ( :i* "o is crimson4 ,?is is ! /> ,r ,leonis4 ,l ,r ,crat]is & ,r ,leporis x is v>iable4 ,next1 let ! obs]v] turn t[>ds ! s\? aga94 ,above ,corvus1 9 ! position %[n 9 ! ,frontispiece1 !re are to be se5 five />s1 =m+ a sort ( wide ,v ) some:at b[$ legs4 ,at ! angle is ! /> gamma ,virg9is1 a not$ d\ble4 ,9 #agef ! compon5ts 7 #f-a_/b seconds ap>t4 ,!y gradually approa*$ till1 9 #ahcf1 !y c\ld n be sep>at$ by ! l>ge/ telescopes4 ,s9ce !n !y h be5 sep>at+1 & !y are n[ #d-a_/b seconds ap>t1 situat$ z %[n 9 ,plate #c4 ,!y are ne>ly equal 9 magnitude 7#d71 & bo? pale yell[4 ,! /> gamma ,leonis is a clos] & m beautiful d\ble4 ,x w be f\nd above ,regulus1 & is ! brighte/ /> on ! blade ( ! ,sickle4 ,! compon5ts are sep>at$ by ab\t #c-a_/e seconds1 ! l>g] ( ! second1 ! small] ( ! f\r? magnitude2 ! =m] yell[-orange1 ! latt] gre5i%-yell[4 ,la/ly1 ! /> iota ,leonis may be tri$4 ,x w be a pretty sev]e te/ = our obs]v]'s telescope1 ! compon5ts be+ only #bd ap>t1 & ! small] sc>cely exce$+ ! eigh? magnitude4 ,! bright] 7f\r? magnitude7 is pale yell[1 ! o!r light blue4 ,,*apt] ,,iv4 ,a ,,half-,,h\r ,,) ,,bootes1 ,,scorpio1 ,,ophiu*us1 ,,etc4 ,we n[ comm5ce a s]ies ( obs]vations suit$ to ! ?ird qu>t] ( ! ye>1 & to ! foll[+ h\rs3--,t5 o'clock on ! #bbnd ( ,july2 n9e on ! #h? ( ,augu/2 eight on ! #bcrd ( ,augu/2 sev5 on ! #h? ( ,octob]2 & int]m$iate h\rs on days int]m$iate to ^!4 ,we look fir/ = ! ,great ,be> t[>ds ! nor?-we/1 & !nce f9d ! ,pole-/>4 ,turn+ t[>ds ! nor? we see ,capella & beta ,aurig l[ d[n & slightly t[>ds ! left ( ! exact nor? po9t4 ,! ,milky ,way crosses ! horizon t[>ds ! nor?-nor?-ea/ & passes to ! opposite po9t ( ! compass1 atta9+ its highe/ po9t above ! horizon t[>ds ea/-s\?-ea/4 ,?is "p ( ! ,milky ,way is well wor? obs]v+1 be+ m>k$ by s+ul> v>iations ( brilliancy4 ,ne> ,arid$ 7! pr9cipal /> ( ,cygnus1 & n[ ly+ due ea/--"s tw5ty-five degrees f ! z5i?7 !re is se5 a /raight d>k rift1 & ne> ?is space is ano!r l>g] cavity1 :i* has be5 t]m$ ! nor!rn ,coal-sack4 ,! space betwe5 gamma1 delta1 & beta ,cygni is cov]$ by a l>ge oval mass1 exce$+ly ri* & brilliant4 ,! neighb\r+ bran*1 ext5d+ f epsilon ,cygni1 is f> less conspicu\s "h1 b ne> ,sagitta becomes bright] ?an ! o!r1 :i* 9 ?is neighb\rhood sudd5ly loses its brilliancy & fad+ gradually beyond ?is po9t becomes invisible ne> beta ,ophiu*i4 ,! cont9u\s /ream becomes pat*y--9 p>ts v brilliant--:]e x crosses ,aquila & ,clypeus4 ,9 ?is neighb\rhood ! o!r /ream reappe>s1 pass+ ov] a region v ri* 9 />s4 ,we see n[ ! greate/ ext5t ( ! ,milky ,way1 t[>ds ?is "p ( its l5g?1 ev] visible 9 our latitudes--j z 9 spr+ we see its greate/ ext5t t[>ds ,monoc]os & ,argo4 ,illu/ration3 ,,plate ,,iv4 ,i may note "h 9 pass+ t ,sir ,john ,h]s*el's del9eation ( ! nor!rn portion ( ! ,milky ,way1 ?\gh a great improvem5t on ! views giv5 9 =m] works1 seems to require revision1 & especially z respects ! v rem>kable pat*es & /reaks :i* *>act]ise ! portion ext5d+ ov] ,cepheus & ,cygnus4 ,x seems to me1 also1 t ! evid5ce on :i* x has be5 urg$ t ! />s compos+ ! ,milky ,way are 7on an av]age7 comp>able 9 magnitude to our own sun1 or to />s ( ! lead+ magnitudes1 is imp]fect4 ,i believe1 = in/ance1 t ! brilliant oval ( milky light 9 ,cygnus comes f />s intimately associat$ ) ! lead+ />s 9 t con/ellation1 & n f> remov$ 9 space 7proportionately7 beyond !m4 ,( c\rse1 if ?is be ! case1 ! />s1 ^: comb9$ light =ms ! pat* ( milky light1 mu/ be f> small] ?an ! lead+ brilliants ( ,cygnus4 ,h[ev]1 ?is is n ! place to ent] on speculations ( ?is sort2 ,i return !re=e to ! bus9ess we h m imm$iately 9 h&4 ,t[>ds ! ea/ is ! squ>e ( ,pegasus l[ d[n t[>ds ! horizon4 ,t[>ds ! s\? is ,scorpio1 di/+ui%$ by ! r$ & brilliant ,ant>es1 & by a tra9 ( conspicu\s />s4 ,t[>ds ! we/ is ,bootes1 8 lead+ brilliant--! ruddy ,arcturus--ly+ some:at ne>] ! horizon ?an ! z5i?1 & slightly s\? ( we/4 ,bootes z a con/ellation is easily f\nd if we rememb] t he is del9eat$ z *as+ away ! ,great] ,be>4 ,?us at pres5t he is se5 9 a slightly incl9$ position1 8 head 7m>k$ by ! ?ird-magnitude /> beta7 ly+ due we/1 "s ?irty degrees f ! z5i?4 ,x has always appe>$ to me1 by ! way1 t ,bootes orig9ally _h nobl] proportions ?an a/ronom]s n[ assign to him4 ,x is kn[n t ,canes ,v5atici n[ occupy ! place ( an uprais$ arm ( ,bootes1 & ,i imag9e t ,corona ,borealis1 ?\gh und\bt$ly a v anci5t con/ellation1 occupies ! place ( 8 o!r arm4 ,giv+ to ! con/ellation ! ext5t ?us impli$1 x exhibits 7bett] ?an mo/ con/ellations7 ! "* assign$ to x4 ,"o c readily picture to oneself ! figure ( a ,h]dsman ) uprais$ arms driv+ ,ursa ,major be=e him4 ,?is view is confirm$1 ,i ?9k1 by ! fact t ! ,arabs call$ ?is con/ellation ! ,vocif]ator4 ,bootes conta9s _m beautiful objects4 ,p>tly on ?is acc\nt1 & p>tly because ?is is a con/ellation ) :i* ! obs]v] %\ld be specially famili>1 a map ( x is giv5 9 ,plate #d4 ,arcturus has a di/ant pale lilac companion1 & is 9 o!r respects a rem>kable & int]e/+ object4 ,x is ( a ruddy yell[ col\r4 ,s*midt1 inde$1 consid]s t ! /> has *ang$ col\r ( late ye>s1 & t :]eas x 0 once v r$ x is n[ a yell[ />4 ,?is op9ion does n seem well gr\nd$1 h[ev]4 ,! /> may h be5 m ruddy once ?an n[1 ?\gh no o!r obs]v] has notic$ su* a peculi>ity2 b x is c]ta9ly n a pure yell[ /> at pres5t 7at any rate z se5 9 our latitude74 ,ow+ probably to ! diff]5ce ( col\r betwe5 ,vega1 ,capella & ,arcturus1 photometricians h n be5 p]fectly agre$ z to ! relative brilliancy ( ^! objects4 ,"s consid] ,vega ! mo/ brilliant /> 9 ! nor!rn heav5s1 :ile o!rs assign ! sup]iority to ,capella4 ,! majority1 h[ev]1 consid] ,arcturus ! lead+ nor!rn brilliant1 & 9 ! :ole heav5s place ?ree only be=e him1 viz41 ,sirius1 ,canopus1 & alpha ,c5tauri4 ,arcturus is rem>kable 9 o!r respects4 ,8 prop] motion is v consid]able1 s great 9 fact t s9ce ! "t ( ,ptolemy ! s\!rly motion 7alone7 ( ,arcturus has c>ri$ him ov] a space ne>ly half z great aga9 z ! moon's app>5t diamet]4 ,"o might expect t s brilliant a />1 app>5tly travell+ at a rate s great comp>$ ) ! av]age prop] motions ( ! />s1 mu/ be comp>atively ne> to u4 ,?is1 h[ev]1 has n be5 f\nd to be ! case4 ,arcturus is1 inde$1 "o ( ! />s ^: di/ance x has be5 f\nd possible to e/imate r\ghly4 ,b he is f\nd to be "s ?ree times z f> f u z ! small /> #fa ,cygni1 & m ?an sev5 times z f> f u z alpha ,c5tauri4 ,! /> delta ,bootis is a wide & unequal d\ble1 ! small] compon5t be+ only ( ! n9? magnitude4 ,above ,alkaid ! la/ /> 9 ! tail ( ! ,great] ,be>1 !re w be notic$ ?ree small />s4 ,^! are !ta1 iota1 & kappa ,bootis1 & are usually plac$ 9 />-maps ne> ! uprais$ h& ( ! ,h]dsman4 ,! two :i* lie next to ,alkaid1 iota & kappa1 are int]e/+ d\bles4 ,! =m] is a wide d\ble 7see ,plate #e71 ! magnitudes ( compon5ts #d & #h1 _! col\rs yell[ & :ite4 ,! l>g] /> ( ?is pair is itself d\ble4 ,! /> kappa ,bootis is n s wide a d\ble 7see ,plate #e71 ! magnitudes ( ! compon5ts #e & #h1 _! col\rs :ite & fa9t blue--a beautiful object4 ,! /> xi ,bootis is an exce$+ly int]e/+ object4 ,x is d\ble1 ! col\rs ( ! compon5ts be+ orange-yell[ & ruddy purple1 _! magnitudes #c-a_/b & #f-a_/b4 ,:5 ?is /> 0 fir/ obs]v$ by ,h]s*el 9 #aghj ! position ( ! compon5ts 0 q diff]5t f t pres5t$ 9 ,plate #e4 ,!y 7 also mu* clos]1 be+ sep>at$ by a di/ance ( less ?an #c-a_/b seconds4 ,s9ce t "t ! small] compon5t has trav]s$ ne>ly a full quadrant1 its di/ance f its prim>y fir/ increas+1 till 9 #ahca ! />s 7 ne>ly #g-a_/b seconds ap>t1 & !nce sl[ly dim9i%+1 s t at pres5t ! />s are less ?an #e seconds ap>t4 ,! p]iod usually assign$ to ! revolution ( ?is b9>y sy/em is #aag ye>s1 & ! p]iod ( p]i-a/ral passage is said to be #aggi4 ,x appe>s to me1 h[ev]1 t ! p]iod %\ld be ab\t #ajh ye>s1 ! epo* ( la/ p]i-a/ral passage #aggg & ( next p]i-a/ral passage1 !re=e1 #ahhe4 ,! angul> motion ( ! second>y r\nd ! prim>y is n[ rapidly increas+1 & ! di/ance betwe5 ! compon5ts is rapidly dim9i%+1 s t 9 a few ye>s a p[]ful telescope w be requir$ to sep>ate ! pair4 ,n f> f xi is pi ,bootis1 repres5t$ 9 ,plate #e z a some:at clos] d\ble1 b 9 reality--n[ at any rate--a slightly wid] pair1 s9ce ! di/ance betwe5 ! compon5ts ( xi has greatly dim9i%$ ( late4 ,bo? ! compon5ts ( pi are :ite1 & _! magnitudes are #c-a_/b & #f4 ,we %all next turn to an exce$+ly beautiful & delicate object1 ! d\ble /> epsilon ,bootis1 kn[n also z ,mirac &1 on acc\nt ( its extreme beauty1 call$ ,pul*]rima by ,admiral ,smy?4 ,! compon5ts ( ?is beautiful d\ble are ( ! ?ird & sev5? magnitude1 ! prim>y orange1 ! second>y sea-gre54 ,! di/ance sep>at+ ! compon5ts is ab\t #c seconds1 p]haps m2 x appe>s to h be5 sl[ly increas+ dur+ ! pa/ t5 or twelve ye>s4 ,smy? assigns to ?is sy/em a p]iod ( revolution ( #ihj ye>s1 b !re c be little d\bt t ! true p]iod is l>gely 9 excess ( ?is e/imate4 ,obs]v]s 9 s\!rn latitudes consid] t ! col\rs ( ! compon5ts are yell[ & blue1 n orange & gre5 z mo/ ( our nor!rn obs]v]s h e/imat$ !m4 ,a little beyond ! l[] left-h& corn] ( ! map is ! /> delta ,s]p5tis1 9 ! position %[n 9 ! ,frontispiece1 ,map #c4 ,?is is ! /> :i* at ! h\r & season depict$ 9 ,map #b =m$ ! upp]mo/ ( a v]tical r[ ( />s1 :i* has n[ assum$ an almo/ horizontal position4 ,! compon5ts ( delta ,s]p5tis are ab\t #c-a_/b seconds ap>t1 _! magnitudes #c & #e1 bo? :ite4 ,! />s !ta#a & !ta#b ,s]p5tis =m a wide d\ble1 ! di/ance betwe5 ! compon5ts be+ #ba-a_/b seconds4 ,!y are ne>ly equal 9 magnitude1 ! prim>y be+ #d-a_/b1 ! second>y #e4 ,bo? are yell[1 ! prim>y be+ ( a pal] yell[ col\r ?an ! small] />4 ,b ! obs]v] may n "k :]e to look = !ta ,s]p5tis1 s9ce x falls 9 a "p ( ! con/ellation q sep>at$ f t "p 9 :i* delta ,s]p5tis lies4 ,9 fact !ta lies on ! extreme ea/]ly v]ge ( ! ea/]n half ( ! con/ellation4 ,x is to be look$ = at ab\t ! same elevation z ! brilliant ,altair1 & 7z to azimu?7 ab\t midway betwe5 ,altair & ! s\?4 ,! />s alpha#a & alpha#b ,libr =m a wide d\ble1 p]haps j sep>able by ! nak$ eye 9 v fav\rable wea!r4 ,! l>g] compon5t is ( ! ?ird1 ! small] ( ! six? magnitude1 ! =m] yell[ ! latt] light grey4 ,! /> beta ,libr is a beautiful light-gre5 /> to ! nak$ eye2 9 ! telescope a wide d\ble1 pale em]ald & light blue4 ,9 ,scorpio !re are sev]al v beautiful objects3-- ,! /> ,ant>es or ,cor ,scorpionis is "o ( ! mo/ beautiful ( ! r$ />s4 ,x has be5 t]m$ ! ,sirius ( r$ />s1 a t]m bett] m]it$ p]haps by ,aldeb>an1 save = ?is t1 9 our latitude1 ,ant>es is1 l ,sirius1 always se5 z a brilliant sc9tillator 7because always l[ d[n71 :]eas ,aldeb>an rises high above ! horizon4 ,ant>es is a d\ble />1 its companion be+ a m9ute gre5 />4 ,9 s\!rn latitudes ! companion ( ,ant>es may be se5 ) a good #d-;in*1 b 9 our latitudes a l>g] op5+ is want$4 ,mr4 ,dawes once saw ! companion ( ,ant>es %9+ alone = sev5 seconds1 ! prim>y be+ hidd5 by ! moon4 ,he f\nd t ! col\r ( ! second>y is n m]ely ! effect ( contra/1 b t ?is small /> is really a gre5 sun4 ,! /> beta ,scorpionis is a f9e d\ble1 ! compon5ts #aca ap>t1 _! magnitudes #b & #e-a_/b1 col\rs :ite & lilac4 ,x has be5 suppos$ t ?is pair is only an optical d\ble1 b a long "t mu/ elapse be=e a decisive op9ion c be pron\nc$ on su* a po9t4 ,! /> sigma ,scorpionis is a wid] b mu* m difficult d\ble1 ! small] compon5t be+ bel[ ! #i? magnitude4 ,! col\r ( ! prim>y 7#d7 is :ite1 t ( ! second>y m>oon4 ,! /> xi ,scorpionis is a neat d\ble1 ! compon5ts #gb ap>t1 _! magnitudes #d-a_/b & #g-a_/b1 _! col\rs :ite & grey4 ,?is /> is really triple1 a fif?-magnitude /> ly+ close to ! prim>y4 ,9 ,ophiu*us1 a con/ellation cov]+ a wide space imm$iately above ,scorpio1 !re are sev]al f9e d\bles4 ,among o!rs-- #ci ,ophiu*i1 di/ance betwe5 compon5ts #aba1 _! magnitudes #e-a_/b & #g-a_/b1 _! col\rs orange & blue4 ,! /> #gj ,ophiu*i1 a f\r?-magnitude /> on ! "r %\ld] ( ,ophiu*us1 is a not$ d\ble4 ,! di/ance betwe5 ! compon5ts ab\t #e-a_/b1 _! magnitudes #d-a_/b & #g1 ! col\rs yell[ & r$4 ,! pair =m a sy/em ^: p]iod ( revolution is ab\t #ie ye>s4 #cf ,ophiu*i 7v>iable71 di/ance #eb1 magnitudes #d-a_/b & #f-a_/b1 col\rs r$ & yell[4 rho ,opiu*i1 di/ance #d1 col\rs yell[ & blue1 magnitudes #e & #g4 ,betwe5 alpha & beta ,scorpionis ! f9e nebula #hj ,m may be look$ =4 7,or m closely ?us3--bel[ beta is ! wide ,d\ble omega#a & omega#b ,scorpionis2 ab\t z f> to ! "r ( ,ant>es is ! /> sigma ,scorpionis1 & imm$iately above ?is is ! fif?-magnitude /> #ai47 ,! nebula we seek lies betwe5 #ai & omega1 ne>] to #ai 7ab\t two-fif?s ( ! way t[>ds omega74 ,?is nebula is describ$ by ,sir ,w4 ,h]s*el z ! ri*e/ & mo/ cond5s$ mass ( />s :i* ! firmam5t (f]s to ! contemplation ( a/ronom]s4 ,!re are two o!r objects conv5i5tly situat$ = obs]vation1 :i* ! obs]v] may n[ turn to4 ,! fir/ is ! great clu/] 9 ! sword-h& ( ,p]seus 7see ,plate #d71 n[ ly+ ab\t #bh above ! horizon betwe5 ,n4,e4 & ,n4,n4,e4 ,! />s gamma & delta ,cassiopei 7see ,map #c ( ,frontispiece7 po9t t[>ds ?is clu/]1 :i* is r f>!r f delta ?an delta f gamma1 & a little s\? ( ! produc$ l9e f ^! />s4 ,! clu/] is well se5 ) ! nak$ eye1 ev5 9 ne>ly full moonlight4 ,9 a telescope ( mod]ate p[] ?is clu/] is a magnific5t object1 & no telescope has yet reveal$ its full glory4 ,! view 9 ,plate #e gives b ! fa9te/ conception ( ! glories ( *i ,p]sei4 ,sir ,w4 ,h]s*el tri$ 9 va9 to gauge ! dep?s ( ?is clu/] ) 8 mo/ p[]ful telescope4 ,he spoke ( ! mo/ di/ant p>ts z s5d+ light to u :i* mu/ h />t$ #djjj or #ejjj ye>s ago4 ,b x appe>s improbable t ! clu/] has 9 reality s enorm\s a longitud9al ext5sion comp>$ ) its transv]se section z ?is view w\ld imply4 ,on ! contr>y1 ,i ?9k we may ga!r f ! appe>ance ( ?is clu/]1 t />s are f> less uni=m 9 size ?an has be5 commonly suppos$1 & t ! m]e irresolvability ( a clu/] is no pro( ( excessive di/ance4 ,x is unlikely t ! fa9te/ compon5t ( ! clu/] is f>!r (f ?an ! brighte/ 7a sev5?-magnitude />7 9 ! proportion ( m ?an ab\t #bj to #ai1 :ile ! ord9>y e/imate ( /> magnitudes1 appli$ by ,h]s*el1 gave a proportion ( #bj or #cj to #a at lea/4 ,i c no m believe t ! compon5ts ( ?is clu/] are />s greatly v>y+ 9 di/ance1 b accid5tally se5 9 ne>ly ! same direction1 7or t !y =m an enorm\sly long sy/em turn$ by accid5t directly t[>ds ! e>?71 ?an ,i c\ld look on ! association ( sev]al ?\s& p]sons 9 ! =m ( a procession z a =tuit\s arrangem5t4 ,next !re is ! great nebula 9 ,&rom$a--kn[n z ! transc5dantly beautiful que5 ( ! nebul4 ,x w n be difficult to f9d ?is object4 ,! />s epsilon & delta ,cassiopei 7,map #c1 ,frontispiece7 po9t to ! /> beta ,&rom$4 ,almo/ 9 a v]tical l9e above ?is /> are two f\r?-magnitude />s mu & gamma1 & close above nu1 a little to ! "r1 is ! object we seek--visible to ! nak$ eye z a fa9t mi/y spot4 ,to tell ! tru?1 ! transc5dantly beautiful que5 ( ! nebul is r a disappo9t+ object 9 an ord9>y telescope4 ,!re is se5 a long oval or l5ticul> spot ( light1 v bright ne> ! c5tre1 especially ) l[ p[]s4 ,b !re is a want ( ! int]e/ atta*+ to ! /range figure ( ! ,great ,orion nebula4 ,! ,&rom$a nebula has be5 p>tially resolv$ by ,"l ,rosse's great reflector1 & 7x is said7 m satisfactorily by ! great refractor ( ,h>v>d ,college4 ,9 ! spectroscope1 ,mr4 ,hugg9s in=ms u1 ! spectrum is peculi>4 ,cont9u\s f ! blue to ! orange1 ! light !re appe>s to cease v abruptly2 !re is no indication ( gaseity4 ,la/ly1 ! obs]v] may turn to ! pair ,miz> & ,alcor1 ! =m] ! middle /> 9 ! ,great ,be>'s tail1 ! latt] #ae' (f4 ,x seems q cle>1 by ! way1 t ,alcor has increas$ 9 brilliancy ( late1 s9ce among ! ,arabians x 0 consid]$ an evid5ce ( v good eyesight to detect ,alcor1 :]eas ?is /> may n[ be easily se5 ev5 9 ne>ly full moonlight4 ,miz> is a d\ble />1 & a f\r? /> is se5 9 ! same field ( view ) ! o!rs 7see ,plate #e74 ,! di/ance betwe5 ,miz> & its companion is #add2 ! magnitude ( ,miz> #c1 ( ! companion #e2 _! col\rs :ite & pale gre51 respectively4 ,,*apt] ,v4 ,a ,,half-,,h\r ,,) ,,&rom$a1 ,,cygnus1 ,,etc4 ,our la/ half-h\r ) ! d\ble />s1 c41 mu/ be a %ort "o1 z we h already ne>ly fill$ ! space allott$ to ^! objects4 ,! obs]vations n[ to be made are suppos$ to take place dur+ ! f\r? qu>t] ( ! ye>1--at t5 o'clock on ,octob] #bcrd2 or at n9e on ,novemb] #g?2 or at eight on ,novemb] #bbnd2 or at sev5 on ,decemb] #f?2 or at h\rs int]m$iate to ^! on int]m$iate days4 ,we look fir/1 z 9 =m] cases1 = ! ,great ,be>1 n[ ly+ l[ d[n t[>ds ! nor?4 ,t[>ds ! nor?-ea/1 a few degrees ea/]ly1 are ! tw9-/>s ,ca/or & ,pollux1 9 a v]tical position1 ,ca/or upp]mo/4 ,above ^!1 a little t[>ds ! "r1 we see ! brilliant ,capella2 & betwe5 ,capella & ! z5i? is se5 ! fe/oon ( ,p]seus4 ,cassiopeia lies ne> ! z5i?1 t[>ds ! nor?1 & ! ,milky ,way ext5ds f ! ea/]n horizon across ! z5i? to ! we/]n horizon4 ,l[ d[n 9 ! ea/ is ,orion1 half ris5 above horizon4 ,turn+ to ! s\?1 we see high up above ! horizon ! squ>e ( ,pegasus4 ,l[ d[n t[>ds ! s\?-s\?-we/ is ,fomalhaut1 po9t$ to by beta & alpha ,pegasi4 ,t[>ds ! we/1 ab\t half-way betwe5 ! z5i? & ! horizon1 is ! noble cross 9 ,cygnus2 bel[ :i*1 t[>ds ! left1 we see ,altair1 & 8 companions beta & gamma ,aquil3 :ile t[>ds ! "r we see ! brilliant ,vega4 ,dur+ ?is half-h\r we %all n conf9e ourselves to any p>ticul> region ( ! heav5s1 b sweep ! mo/ conv5i5tly situat$ con/ellations4 ,illu/ration3 ,,plate ,v4 ,fir/1 h[ev]1 we %\ld recomm5d ! obs]v] to try & get a good view ( ! great nebula 9 ,&rom$a1 :i* is n conv5i5tly situat$ = obs]vation1 b is s high t aft] a little tr\ble ! obs]v] may expect a m di/9ct view ?an 9 ! previ\s qu>t]4 ,he w see beta ,&rom$ t[>ds ! s\?-ea/1 ab\t #ah f ! z5i?1 mu & nu ne>ly 9 a l9e t[>ds ! z5i?1 & ! nebula ab\t half-way betwe5 beta & ! z5i?4 ,) a simil> object x w be well to take ano!r view ( ! great clu/] 9 ,p]seus1 ab\t #ah f ! z5i? t[>ds ! ea/-nor?-ea/ 7see ! po9t]s gamma & delta ,cassiopei 9 ,map #d1 ,frontispiece71 ! clu/] be+ betwe5 delta ,cassiopei & alpha ,p]sei4 ,n v f> (f is ! wond]ful v>iable ,algol1 n[ due ea/1 & ab\t #eh above ! horizon4 ,! v>iability ( ?is celebrat$ object 0 d\btless discov]$ 9 v anci5t times1 s9ce ! "n ,al-gol1 or ! ,demon seems to po9t to a k ( ! peculi>ity ( ?is sl[ly w9k+ eye4 ,to ,goodricke1 h[ev]1 is due ! r$iscov]y ( ,algol's v>iability4 ,! p]iod ( v>iation is #b;d4 #bj;h4 #dhm42 dur+ #b;h4 #adm4 ,algol appe>s ( ! second magnitude2 ! rema9+ #f-c_/d h\rs are occupi$ by ! gradual decl9e ( ! /> to ! f\r? magnitude1 & its equally gradual return to ! second4 ,x w be f\nd easy to wat* ! v>iations ( ?is s+ul> object1 ?\gh1 ( c\rse1 _m ( ! m9ima are atta9$ 9 ! daytime4 ,! foll[+ may help ! obs]v]3-- ,on ,octob] #h?1 #ahfg1 at ab\t half-pa/ elev5 9 ! ev5+1 ,i notic$ t ,algol _h rea*$ its m9imum ( brilliancy4 ,h5ce ! next m9imum 0 atta9$ at ab\t a qu>t]-pa/ eight on ! ev5+ ( ,octob] #aa?2 ! next at ab\t five on ! ev5+ ( ,octob] #ad?1 & s on4 ,n[1 if ?is process be c>ri$ on1 x w be f\nd t ! next ev5+ m9imum occurr$ at ab\t #aj;h4 7circit]7 on ! ev5+ ( ,octob] #ca/1 ! next at ab\t #aa;h4 #cjm4 on ! ev5+ ( ,novemb] #bj?4 ,?us at :atev] h\r any m9imum occurs1 ano!r occurs six weeks & a day lat]1 at ab\t ! same h\r4 ,?is w\ld be exact en\gh if ! p]iod ( v>iation 7 exactly #b;d4 #bjm4 #dhs41 b ! p]iod is ne>ly a m9ute great]1 & z !re are fifte5 p]iods 9 six weeks & a day1 x results t !re is a diff]5ce ( ab\t #acm4 9 ! "t at :i* ! successive recurr5ces at ne>ly ! same h\r take place4 ,h5ce we are able to draw up ! two foll[+ ,tables1 :i* w suffice to give all ! m9ima conv5i5tly obs]vable dur+ ! next two ye>s4 ,/>t+ f a m9imum at ab\t #aa;h4 #dem4 on ,novemb] #bj?1 #ahfg1 & notic+ t ! next #dc-;day p]iod 7) ! #acm4 add$7 gives u an obs]vation at midnight on ,janu>y #bnd1 #ahfh1 & t successive p]iods w\ld make ! h\r lat] yet1 we take ! m9imum next aft] t ( ,janu>y #bnd1 viz4 t ( ,janu>y #e?1 #ahfh1 #h;h4 #dhm41 & tak+ #dc-;day p]iods 7) #acm4 add$ to ea*71 we get ! s]ies-- h4 m4 ,jan4 #e1 #ahfh1 #h #de ,p4,m4 ,feb4 #ag1 ----1 #h #eh ---- ,m>4 #ca1 ----1 #i #aa ---- ,may #ac1 ----1 #i #bd ---- ,june #be1 ----1 #i #cg ---- ,aug4 #g1 ----1 #i #ej ---- ,sept4 #ai1 ----1 #aj #c ---- ,nov4 #a ----1 #aj #af ---- ,dec4 #ad1 ----1 #aj #bi ---- ,jan4 #bf1 #ahfi1 #aj #db ---- ,m>4 #aj1 ----1 #aj #be ---- ,m>4 #ac1 ----1 #g #dc ----#g ,apr4 #be1 ----1 #g #ef ---- ,june #g1 ----1 #h #i ---- ,july #bj1 ----1 #h #bb ---- ,sept4 #a1 ----1 #h #ce ---- ,oct4 #ad1 ----1 #h #dh ---- ,nov4 #bf1 ----1 #i #a ---- ,jan4 #h1 #ahgj1 #i #ad ---- ,feb4 #bj1 ----1 #i #bg ---- ,f ! m9imum at ab\t #aj ,p4,m4 on ,octob] #ca/1 #ahfg1 we get 9 l mann] ! s]ies-- h4 m4 ,dec4 #ac1 #ahfg1 #aj #ac ,p4,m4 ,jan4 #be1 #ahfh1 #aj #bf ---- ,m>4 #h1 ----1 #aj #ci ---- ,apr4 #bj1 ----1 #aj #eb ---- ,june #b1 ----1 #aa #e ---- ,june #e1 ----1 #g #ec ----#h ,july #ah1 ----1 #h #f ---- ,aug4 #cj1 ----1 #h #ai ---- ,oct4 #ab1 ----1 #h #cb ---- ,nov4 #bd1 ----1 #h #de ---- ,jan4 #f1 #ahfi1 #h #eh ---- ,feb4 #ah1 ----1 #i #aa ---- ,apr4 #b1 ----1 #i #bd ---- ,may #ae1 ----1 #i #cg ---- ,june #bg1 ----1 #i #ej ---- ,aug4 #i1 ----1 #aj #c ---- ,sept4 #ba1 ----1 #aj #af ---- ,nov4 #c1 ----1 #aj #bi ---- ,dec4 #af1 ----1 #aj #db ---- ,jan4 #bh1 #ahgj1 #aj #ee ---- ,f "o or o!r ( ^! tables e obs]vable m9imum c be obta9$4 ,?us1 suppose ! obs]v] wants to look = a m9imum dur+ ! la/ =tnight 9 ,augu/1 #ahfh4 ,! fir/ table gives him no in=mation1 ! latt] gives him a m9imum at #h;h4 #aim4 ,p4,m4 on ,augu/ #cj2 h5ce ( c\rse !re is a m9imum at #aa;h4 #cam4 ,p4,m4 on ,augu/ #bg2 & !re are no o!r conv5i5tly obs]vable m9ima dur+ ! =tnight 9 "q4 ,! cause ( ! rem>kable v>iation 9 ?is />'s brilliancy has be5 assign$ by "s a/ronom]s to ! pres5ce ( an opaque second>y1 :i* transits ,algol at regul> int]vals2 o!rs h adopt$ ! view t ,algol is a lum9\s second>y1 revolv+ ar\nd an opaque prim>y4 ,( ^! views ! =m] seems ! mo/ natural & satisfactory4 ,x po9ts to a second>y ^: mass be>s a f> great] proportion to t ( ! prim>y1 ?an ! mass ev5 ( ,jupit] be>s to ! sun2 ! %ortness ( ! p]iod is also rem>kable4 ,x may be notic$ t obs]vation po9ts to a gradual dim9ution 9 ! p]iod ( ,algol's v>iation1 & ! dim9ution seems to be proce$+ m & m rapidly4 ,h5ce 7assum+ ! exi/5ce ( a d>k second>y7 we mu/ suppose t ei!r x travels 9 a resi/+ m$ium :i* is gradually de/roy+ its motion1 or t !re are o!r dep5d5t orbs ^: attractions affect ! p]iod ( ?is second>y4 ,9 ! latt] case ! decrease 9 ! p]iod w atta9 a limit & be foll[$ by an increase4 ,h[ev]1 int]e/+ z ! subject may be1 x is a digression f telescopic "w1 to :i* we n[ return4 ,)9 ! conf9es ( ! second map 9 ,plate #d is se5 ! f9e /> gamma ,&rom$4 ,at ! h\r ( our obs]vations x lies high up t[>ds ,e4,s4,e4 ,x is se5 z a d\ble /> ) v mod]ate telescopic p[]1 ! di/ance betwe5 ! compon5ts be+ upw>ds ( #aj2 _! magnitudes #c & #e-a_/b1 _! col\rs orange & gre54 ,p]haps !re is no m int]e/+ d\ble visible ) l[ p[]s4 ,! small] /> is aga9 d\ble 9 fir/-class telescopes1 ! compon5ts be+ yell[ & blue accord+ to "s obs]v]s1 b accord+ to o!rs1 bo? gre54 ,bel[ gamma ,&rom$ lie ! />s beta & gamma ,triangulorum1 gamma a f9e nak$-eye triple 7! companions be+ delta & eta ,triangulorum71 a f9e object ) a v l[ p[]4 ,to ! "r is alpha ,triangulorum1 c]ta9ly less brilliant ?an beta4 ,bel[ alpha are ! ?ree />s alpha1 beta1 & gamma ,arietis1 ! fir/ an unequal & difficult d\ble1 ! companion be+ purple1 & only j visible 7"u fav\rable circum/ances7 ) a good #c-;in* telescope2 ! la/ an easy d\ble1 int]e/+ z be+ ! fir/ ev] discov]$ 7by ,hook1 9 #affd71 ! col\rs ( compon5ts :ite & grey4 ,imm$iately bel[ alpha ,arietis is ! /> alpha ,ceti1 t[>ds ! "r ( :i* 7a little l[]7 is ,mira1 a wond]ful v>iable4 ,?is /> has a p]iod ( #cca-a_/c days2 dur+ a =tnight x appe>s z a /> ( ! #bnd magnitude1--on ea* side ( ?is =tnight !re is a p]iod ( ?ree mon?s dur+ "o ( :i* ! /> is increas+1 :ile dur+ ! o!r x is dim9i%+ 9 brightness3 dur+ ! rema9+ five mon?s ( ! p]iod ! /> is invisible to ! nak$ eye4 ,!re are _m peculi>ities & *anges 9 ! v>iation ( ?is />1 into :i* space w n p]mit me to ent]4 ,imm$iately above ,mira is ! /> alpha ,piscium at ! knot ( ! ,fi%es' connect+ b&4 ,?is is a f9e d\ble1 ! di/ance betwe5 ! compon5ts be+ ab\t #c-a_/b1 _! magnitudes #e & #f1 _! col\rs pale gre5 & blue 7see ,plate #e74 ,close to gamma ,aqu>ii 7see ,frontispiece1 ,map #d71 above & to ! left ( x1 is ! int]e/+ d\ble zeta ,aqu>ii2 ! di/ance betwe5 ! compon5ts is ab\t #c-a_/b1 _! magnitudes #d & #d-a_/b1 bo? :iti% yell[4 ,! p]iod ( ?is b9>y seems to be ab\t #gej ye>s4 ,turn+ next t[>ds ! s\?-we/ we see ! second-magnitude /> epsilon ,pegasi1 "s #dj above ! horizon4 ,?is /> is a wide b n easy d\ble1 ! second>y be+ only ( ! n9? magnitude2 its col\r is lilac1 t ( ! prim>y be+ yell[4 ,t[>ds ! "r ( epsilon ,pegasi & l[] d[n are se5 ! ?ree f\r?-magnitude />s :i* m>k ! con/ellation ,equuleus4 ,( ^! ! l[e/ is alpha1 to ! "r ( :i* lies epsilon ,equulei1 a fif?-magnitude />1 really triple1 b se5 z a d\ble /> ) ord9>y telescopes 7,plate #e74 ,! di/ance betwe5 ! compon5ts is ne>ly #aa1 _! col\rs :ite & blue1 _! magnitudes #e-a_/b & #g-a_/b4 ,! prim>y is a v close d\ble1 :i* appe>s1 h[ev]1 to be op5+ out r rapidly4 ,imm$iately bel[ ,equuleus are ! />s alpha#a & alpha#b ,capricorni1 se5 z a nak$-eye d\ble to ! "r ( & above beta4 ,bo? alpha#a & alpha#b are yell[2 alpha#b is ( ! #crd1 alpha#a ( ! #d? magnitude2 9 a good telescope five />s are se51 ! o!r ?ree be+ blue1 a%-col\r$1 & lilac4 ,! /> beta ,capricorni is also a wide d\ble1 ! compon5ts yell[ & blue1 ) _m telescopic companions4 ,to ! "r ( ,equuleus1 t[>ds ! we/-s\?-we/ is ! con/ellation ,delph9us4 ,! upp] left-h& /> ( ! rhombus ( />s =m+ ! head ( ! ,delph9us is ! /> gamma ,delph9i1 a r easy d\ble 7see ,plate #e71 ! compon5ts be+ ne>ly #ab ap>t1 _! magnitudes #d & #g1 _! col\rs gold5 yell[ & flu%$ grey4 ,turn we next to ! *>m+ d\ble ,albireo1 on ! beak ( ,cygnus1 ab\t #cf above ! horizon t[>ds ! we/4 ,! compon5ts are #cd-a_/b ap>t1 _! magnitudes #c & #f1 _! col\rs orange-yell[1 & blue4 ,x has be5 suppos$ 7p]haps on insuffici5t evid5ce7 t ?is /> is m]ely an optical d\ble4 ,x mu/ always be rememb]$ t a c]ta9 proportion ( />s 7among/ ^? sep>at$ by s consid]able a di/ance7 mu/ be optically comb9$ only4 ,! /> *i ,cygni is a wide d\ble 7v>iable7 />4 ,! compon5ts are sep>at$ by ne>ly #bf1 _! magnitudes #e & #i1 _! col\rs yell[ & light blue4 *i may be f\nd by notic+ t !re is a clu/] ( small />s 9 ! middle ( ! triangle =m$ by ! />s gamma1 delta1 & beta ,cygni 7see ,map #d1 ,frontispiece71 & t *i is ! ne>e/ /> ( ! clu/] to beta4 ,! /> phi ,cygni1 :i* is j above & v close to beta 7,albireo71 does n belong to ! clu/]4 *i is ab\t half z f> aga9 f phi z phi f ,albireo4 ,b z *i desc5ds to ! #aa? magnitude at its m9imum ! obs]v] mu/ n always expect to f9d x v easily4 ,x has be5 kn[n to be invisible at ! epo* :5 x %\ld h be5 mo/ conspicu\s4 ,! p]iod ( ?is v>iable is #djf days4 ,! /> #fa ,cygni is an int]e/+ "o4 ,s f> z obs]vation has yet ext5d$1 x w\ld seem to be ! ne>e/ to u ( all />s visible 9 ! nor!rn hemisph]e4 ,x is a f9e d\ble1 ! compon5ts ne>ly equal 7#e-a_/b & #f71 bo? yell[1 & ne>ly #ai ap>t4 ,! p]iod ( ?is b9>y appe>s to be ab\t #edj ye>s4 ,to f9d #fa ,cygni note t epsilon & delta ,cygni =m ! diamet] ( a semicircle divid$ into two quadrants by alpha ,cygni 7,arid$74 ,on ?is semicircle1 on ei!r side ( alpha1 lie ! />s nu & alpha ,cygni1 nu t[>ds epsilon4 ,n[ a l9e f alpha to nu produc$ passes v ne> to #fa ,cygni at a di/ance f nu some:at great] ?an half ! di/ance ( nu f alpha4 ,! /> mu ,cygni lies 9 a corn] ( ! con/ellation1 r f>!r f zeta ?an zeta f epsilon ,cygni4 ,a l9e f epsilon to zeta produc$ meets kappa ,pegasi1 a f\r?-magnitude />2 & mu ,cygni1 a fif?-magnitude />1 lies close above kappa ,pegasi4 ,! di/ance betwe5 ! compon5ts is ab\t #e-a_/b1 _! magnitudes #e & #f1 _! col\rs :ite & pale blue4 ,! /> psi ,cygni may next be look$ =1 b = ?is a good map ( ,cygnus w be want$1 z psi is n po9t$ to by any well-m>k$ />s4 ,a l9e f alpha1 p>allel to ! l9e jo9+ gamma & delta1 & ab\t "o-?ird long] ?an t l9e1 w\ld ab\t m>k ! position ( psi ,cygni4 ,! di/ance betwe5 ! compon5ts ( ?is d\ble is ab\t #c-a_/b1 _! magnitudes #e-a_/b & #h1 _! col\rs :ite & lilac4 ,la/ly1 ! obs]v] may turn to ! />s gamma#a & gamma#b ,draconis t[>ds ! nor?-we/ ab\t #dj above ! horizon 7!y are includ$ 9 ! second map ( ,plate #b74 ,!y =m a wide d\ble1 hav+ equal 7fif?-magnitude7 compon5ts1 bo? grey4 7,see ,plate #e47 ,,*apt] ,,vi4 ,,half-,,h\rs ,,) ,,! ,,planets4 ,9 obs]v+ ! />s1 we c select a "p ( ! heav5s :i* may be conv5i5tly obs]v$2 & 9 ?is way 9 ! c\rse ( a ye> we c obs]ve e "p ( ! heav5s visible 9 our nor!rn hemisph]e4 ,b ) ! planets ! case is n q s simple4 ,!y come into view at no fix$ season ( ! ye>3 "s ( !m c nev] be se5 by night on ! m]idian2 & !y all %ift _! place among ! />s1 s t we require "s me?od ( det]m9+ :]e to look = !m on any p>ticul> night1 & ( recognis+ !m f neighb\r+ fix$ />s4 ,! regul> obs]v] w ( c\rse make use ( ! ',nautical ,almanac'2 b ',dietri*s5 & ,hannay's ,almanac' w s]ve e purpose ( ! amateur telescopi/4 ,i w briefly describe ^? p>ts ( ! almanac :i* are useful to ! obs]v]4 ,x w be f\nd t ?ree pages are assign$ to ea* mon?1 ea* page giv+ diff]5t in=mation4 ,if we call ^! pages ,i4 ,,ii4 ,,iii41 !n 9 ord] t page ,i4 = ea* mon? may fall to ! left ( ! op5 d\ble page1 & also t ,i4 & ,,ii4 may be op5 toge!r1 ! pages are arrang$ 9 ! foll[+ ord]3 ,i4 ,,ii4 ,,iii42 ,,iii4 ,i4 ,,ii42 ,i4 ,,ii4 ,,iii42 & s on4 ,n[ page ,,iii4 = any mon? does n conc]n ! amateur obs]v]4 ,x gives in=mation conc]n+ ! moon's motions1 :i* is valuable to ! sailor1 & int]e/+ to ! /ud5t ( a/ronomy1 b n applicable to amateur obs]vation4 ,illu/ration3 ,,plate ,,vi4 ,we h !n only pages ,i4 & ,,ii4 to consid]3-- ,across ! top ( bo? pages ! "r asc5sion & decl9ation ( ! planets ,v5us1 ,jupit]1 ,m>s1 ,saturn1 ,m]cury1 & ,uranus are giv51 accompani$ by ^? ( two conspicu\s />s4 ,?is in=mation is v valuable to ! telescopi/4 ,9 ! fir/ place1 z we %all pres5tly see1 x %[s him :at planets are well situat$ = obs]vation1 & secondly x enables him to map d[n ! pa? ( any planet f day to day among ! fix$ />s4 ,?is is a v useful ex]cise1 by ! way1 & also a v in/ructive "o4 ,! /ud5t may ei!r make use ( ! regul> maps & m>k d[n ! planet's pa? 9 p5cil1 tak+ a light curve ?r\gh ! po9ts giv5 by ! data 9 8 almanac1 or he may lay d[n a set ( m]idians suit$ to ! "p ( ! heav5s trav]s$ by ! planet1 & !n proce$ to m>k 9 ! planet's pa? & ! />s1 tak+ ! latt] ei!r f 8 maps or f a conv5i5t li/ ( />s4#i ,my ',h&book ( ! ,/>s' has be5 con/ruct$ to aid ! /ud5t 9 ^! processes4 ,x mu/ be notic$ t old maps are n suit$ = ! "w1 because1 ?r\gh precession1 ! />s are all out ( place z respects ,r4,a4 & ,dec4 ,ev5 ! ,society's maps1 con/ruct$ s z to be "r = #ahcj1 are beg9n+ to be out ( date4 ,b a matt] ( #bj or #cj ye>s ei!r way is n important4#aj ,my ,maps1 ,h&book & ,zodiac-*>t h be5 con/ruct$ = ! ye> #ahhj1 s z to be s]viceable = ! next fifty ye>s or s4 ,next1 bel[ ! table ( ! planets1 we h a set ( v]tical columns4 ,^! are1 9 ord]1 ! days ( ! mon?1 ! cal5d>--9 :i* are includ$ "s a/ronomical notices1 among/ o!rs ! diamet] ( ,saturn on diff]5t dates1 ! h\rs at :i* ! sun rises & sets1 ! sun's "r asc5sion1 decl9ation1 diamet]1 & longitude2 !n eight columns :i* d n conc]n ! obs]v]2 aft] :i* come ! h\rs at :i* ! moon rises & sets1 ! moon's age2 & la/ly 7s f> z ! obs]v] is conc]n$7 an important column ab\t ,jupit]'s sy/em ( satellites4 ,next1 we h1 at ! foot ( ! fir/ page1 ! h\rs at :i* ! planets rise1 s\?1 & set2 & at ! foot ( ! second page we h ! dates ( conjunctions1 oppositions1 & ( o!r ph5om5a1 ! diamet]s ( ,v5us1 ,jupit]1 ,m>s1 & ,m]cury1 & f9ally a few words respect+ ! visibility ( ^! f\r planets4 ,aft] ! ?irty-six pages assign$ to ! mon?s foll[ f\r 7pp4 #db-df7 9 :i* mu* important a/ronomical in=mation is conta9$2 b ! po9ts :i* mo/ conc]n our obs]v] are 7i47 a small table %[+ ! appe>ance ( ,saturn's r+s1 & 7ii47 a table giv+ ! h\rs at :i* ,jupit]'s satellites are occult$ or eclips$1 re-appe>1 c4 ,we w n[ take ! planets 9 ! ord] ( _! di/ance f ! sun3 we %all see t ! in=mation giv5 by ! almanac is v important to ! obs]v]4 ,m]cury is s close to ! sun z to be r>ely se5 ) ! nak$ eye1 s9ce he nev] sets mu* m ?an two h\rs & a few m9utes aft] ! sun1 or rises by m ?an t int]val be=e ! sun4 ,x mu/ n be suppos$ t at ea* successive epo* ( mo/ fav\rable appe>ance ,m]cury sets s long aft] ! sun or rises s long be=e him4 ,x w\ld occupy too mu* ( our space to ent] into ! circum/ances :i* affect ! l5g? ( ^! int]vals4 ,! "q1 9 fact1 is n a v simple "o4 ,all ! necess>y in=mation is giv5 9 ! almanac4 ,we m]ely notice t ! planet is mo/ fav\rably se5 z an ev5+ /> 9 spr+1 & z a morn+ /> 9 autumn4#aa ,! obs]v] ) an equatorial has ( c\rse no difficulty 9 f9d+ ,m]cury1 s9ce he c at once direct 8 telescope to ! prop] po9t ( ! heav5s4 ,b ! obs]v] ) an alt-azimu? might fail = ye>s toge!r 9 obta9+ a sight ( ?is int]e/+ planet1 if he tru/$ to unaid$ nak$-eye obs]vations 9 look+ = him4 ,cop]nicus nev] saw ,m]cury1 ?\gh he (t5 look$ = him2 & ,mr4 ,h9d tells me he has se5 ! planet b once ) ! nak$ eye--?\gh ?is p]haps is n a v rem>kable circum/ance1 s9ce ! sy/ematic work] 9 an obs]vatory seldom has occasion to obs]ve objects ) ! unaid$ eye4 ,by ! foll[+ me?od ! obs]v] c easily pick up ! planet4 ,across two uprights 7,fig4 #aj7 nail a /raight rod1 s t :5 look$ at f "s fix$ po9t ( view ! rod may correspond to ! sun's pa? ne> ! "t ( obs]vation4 ,! rod %\ld be at "r-angles to ! l9e ( sight to its c5tre4 ,fa/5 ano!r rod at "r angles to ! fir/4 ,f ! po9t at :i* ! rods cross measure (f & m>k on bo? rods spaces ea* subt5d+ a degree z se5 f ! po9t ( view4 ,?us1 if ! po9t ( view is #i-a_/b feet (f1 ^! spaces mu/ ea* be #b in*es long1 & !y mu/ be proportionately less or great] z ! eye is ne>] or f>!r4 ,illu/ration3 ,fig4 #aj4 ,n[ suppose ! obs]v] wi%es to view ,m]cury on "s day1 :]eon ,m]cury is an ev5+ />4 ,take1 = in/ance1 ,june #i?1 #ahfh4 ,we f9d f ',dietri*s5' t on ?is day 7at noon7 ,m]cury's ,r4,a4 is #f;h4 #ecm4 #bcs43 & ! sun's #e;h4 #aam4 #cas4 ,we ne$ n tr\ble ourselves ab\t ! odd h\rs aft] noon1 & ?us we h ,m]cury's ,r4,a4 great] ?an ! sun's by #a;h4 #dam4 #ebs4 ,n[ we w suppose t ! obs]v] has s fix$ 8 uprights & ! two rods1 t ! sun1 se5 f ! fix$ po9t ( view1 appe>s to pass ! po9t ( cross+ ( ! rods at half-pa/ sev51 !n ,m]cury w pass ! cross-rod at #aam4 #ebs4 pa/ n9e4 ,b :]e8 ,to le>n ?is we mu/ take out ,m]cury's decl9ation1 :i* is #bd #dc' #ah ,n41 & ! sun's1 :i* is #bb #ei' #aj ,n4 ,! diff]5ce1 #a #dd' #h ,n4 gives u ,m]cury's place1 :i* x appe>s is r less ?an #a-c_/d degree nor? ( ! sun4 ,?us1 ab\t #a;h4 #dbm4 aft] ! sun has pass$ ! cross-rod1 ,m]cury w pass x betwe5 ! fir/ & second divisions above ! po9t ( fa/5+4 ,! sun w h set ab\t an h\r1 & ,m]cury w be easily f\nd :5 ! telescope is direct$ t[>ds ! place indicat$4 ,x w be notic$ t ?is me?od does n require ! "t to be exactly kn[n4 ,all we h to d is to note ! mom5t at :i* ! sun passes ! po9t ( fa/5+ ( ! two rods1 & to take our #a;h4 #dbm4 f t mom5t4 ,?is me?od1 x may be notic$ 9 pass+1 may be appli$ to give nak$-eye obs]vations ( ,m]cury at prop] seasons 7giv5 9 ! almanac74 ,by a little +5uity x may be appli$ z well to morn+ z to ev5+ obs]vations1 ! sun's passage ( ! cross-rod be+ tak5 on "o morn+ & ,m]cury's on ! next1 s _m m9utes be=e ! h\r ( ! fir/ obs]vation4 ,9 ?is way sev]al views ( ,m]cury may be obta9$ dur+ ! ye>4 ,su* me?ods may appe> v insignificant to ! sy/ematic obs]v] ) ! equatorial1 b t !y are effective ,i c ass]t f my own exp]i5ce4 ,simil> me?ods may be appli$ to det]m9e f ! position ( a kn[n object1 t ( any neighb\r+ unkn[n object ev5 at night4 ,! cross-rod mu/ be %ift$ 7or else two cross-rods us$7 :5 ! unkn[n prec$es ! kn[n object4 ,if two cross-rods are us$1 acc\nt mu/ be tak5 ( ! gradual dim9ution 9 ! l5g? ( a degree ( "r asc5sion z we leave ! equator4 ,ev5 simpl] me?ods c>efully appli$ may s]ve to give a view ( ,m]cury4 ,to %[ ?is1 ,i may describe h[ ,i obta9$ my fir/ view ( ?is planet4 ,on ,june #a/1 #ahfc1 ,i notic$1 t at five m9utes pa/ sev5 ! sun1 z se5 f my /udy w9d[1 appe>$ f beh9d ! gable-end ( ,mr4 ,/4 ,aubyn's h\se at ,/oke1 ,devon4 ,i e/imat$ ! effect ( ,m]cury's nor!rly decl9ation 7diff]5t ( c\rse = a v]tical wall1 ?an = ! cross-rod 9 fig4 #h1 :i*1 9 fact1 agrees ) a decl9ation-circle71 & f\nd t he w\ld pass out opposite a p>ticul> po9t ( ! wall a c]ta9 "t aft] ! sun4 ,i !n turn$ ! telescope t[>ds t po9t1 & focuss$ = di/9ct vision ( di/ant objects1 s t ! outl9e ( ! h\se 0 se5 out ( focus4 ,z ! calculat$ "t ( app>ition approa*$1 ,i mov$ ! telescope up & d[n s t ! field swept ! neighb\rhood ( ! e/imat$ po9t ( app>ition4 ,i ne$ h>dly say t ,m]cury did n appe> exactly at ! assign$ po9t1 nor did ,i see him make 8 fir/ appe>ance2 b ,i pick$ him up s soon aft] em]g5ce t ! outl9e ( ! h\se 0 9 ! field ( view ) him4 ,he appe>$ z a half-disc4 ,i foll[$ him ) ! telescope until ! sun _h set1 & soon aft] ,i 0 able to see him v di/9ctly ) ! nak$ eye4 ,he %one ) a peculi> brilliance on ! /ill bright sky2 b al?\gh p]fectly di/9ct to ! view :5 8 place 0 indicat$1 he escap$ detection by ! undirect$ eye4#ab ,m]cury does n pres5t any features ( great int]e/ 9 ord9>y telescopes2 ?\gh he usually appe>s bett] def9$ ?an ,v5us1 at lea/ z ! latt] is se5 on a d>k sky4 ,! phases are pleas+ly se5 7z %[n 9 ,plate #f7 ) a telescope ( mod]ate p[]4 ,= _! prop] obs]vation1 h[ev]1 ! planet mu/ be look$ = ) ! telescope 9 ! mann] above indicat$1 z he always %[s a ne>ly semi-circul> disc :5 he is visible to ! nak$ eye4 ,we come next to ,v5us1 ! mo/ spl5did ( all ! planets to ! eye4 ,9 ! telescope ,v5us disappo9ts ! obs]v]1 h[ev]4 ,h] int5se lu/re br+s out e defect ( ! in/rum5t1 & especially ! *romatic ab]ration4 ,a d>k glass (t5 improves ! view1 b n always4 ,besides1 an int]pos$ glass has an unpleasant effect on ! field ( view4 ,p]haps ! be/ me?od ( obs]v+ ,v5us is to se>* = h] :5 %e is /ill high above ! horizon1 & :5 !re=e ! backgr\nd ( ! sky is bright en\gh to take (f ! planet's gl>e4 ,! me?od ,i h describ$ = ! obs]vation ( ,m]cury w prove v useful 9 ! se>* = ,v5us :5 ! sun is above ! horizon or b j set4 ,( c\rse1 :5 an object is to be look$ = high above ! horizon1 ! two rods :i* support ! cross-rods mu/ n be upright1 b squ>e to ! l9e ( view to t "p ( ! sky4 ,b ! obs]v] mu/ n expect to see mu* dur+ 8 obs]vation ( ,v5us4 ,9 fact1 he c sc>cely d m ?an note h] v>y+ phases 7see ,plate #f7 & ! some:at unev5 b\nd>y ( ! t]m9ator4 ,our lead+ obs]v]s h done s little ) ?is fasc9at+ b disappo9t+ planet1 t amateurs mu/ n be surpris$ at _! own failure4 ,i suppose ! "q :e!r ,v5us has a satellite1 or at any rate :e!r ! object suppos$ to h be5 se5 by ,cass9i & o!r old obs]v]s 7 a satellite1 mu/ be consid]$ z decid$ 9 ! negative4 ,t ,cass9i %\ld h se5 an object :i* ,dawes & ,webb h fail$ to see mu/ be consid]$ utt]ly improbable4 ,leav+ ! inf]ior planets1 we come to a s]ies ( important & int]e/+ objects4 ,fir/ we h ! planet ,m>s1 ne>ly ! la/ 9 ! scale ( planet>y magnitude1 b f> f be+ ! lea/ int]e/+ ( ! planets4 ,x is 9 fact q c]ta9 t we obta9 a bett] view ( ,m>s ?an ( any object 9 ! heav5s1 save ! ,moon alone4 ,he may pres5t a less di/+ui%$ appe>ance ?an ,jupit] or ,saturn1 b we see 8 surface on a l>g] scale ?an t ( ei!r ( ^? giant orbs1 ev5 if we assume t we ev] obta9 a fair view ( _! real surface4 ,nor ne$ ! mod]ately arm$ obs]v] despair ( obta9+ int]e/+ views ( ,m>s4 ,! telescope ) :i* ,be] & ,mdl] made _! celebrat$ s]ies ( views 0 only a #d-;in* "o1 s t ) a #c-;in* or ev5 a #b-;in* ap]ture ! att5tive obs]v] may expect int]e/+ views4 ,9 fact1 m dep5ds on ! obs]v] ?an on ! in/rum5t4 ,a pati5t & att5tive scrut9y w reveal features :i* at ! fir/ view :olly escape notice4 ,9 ,plate #f ,i h giv5 a s]ies ( views ( ,m>s mu* m di/9ct ?an an obs]v] may expect to obta9 ) mod]ate p[]s4 ,i add a *>t ( ,m>s1 a m9iature ( "o ,i h prep>$ f a *>m+ s]ies ( trac+s suppli$ me by ,mr4 ,dawes4 ,! views tak5 by ?is celebrat$ obs]v] 9 #aheb1 #ahef1 #ahfj1 #ahfb1 & #ahfd1 are f> bett] ?an any o!rs ,i h se54 ,! views by ,be] & ,mdl] are good1 z are "s ( ,sec*i's 7?\gh !y appe> badly drawn71 ,nasmy?'s & ,phillips'2 ,del>ue's two views are also admirable2 & ,locky] has giv5 a bett] set ( views ?an any ( ! o!rs4 ,b !re is an am\nt ( detail 9 ,mr4 ,dawes' views :i* r5d]s !m sup]ior to any yet tak54 ,i mu/ confess ,i fail$ at a fir/ view to see ! full value ( ,mr4 ,dawes' trac+s4 ,fa9t m>ks appe>$1 :i* ,i suppos$ to be m]ely int5d$ to repres5t %ad+s sc>cely se54 ,a m c>eful /udy %ew$ me t e m>k is to be tak5 z ! repres5tative ( :at ,mr4 ,dawes actually saw4 ,! consi/5cy ( ! views is p]fectly wond]ful1 :5 comp>$ ) ! vagu5ess & inconsi/5cy obs]vable 9 ne>ly all o!r views4 ,& ?is consi/5cy is n %[n by m]e resemblance1 :i* might h be5 an effect r ( memory 7unconsci\sly ex]t$7 ?an obs]vation4 ,! same feature *anges s mu* 9 figure1 z x appe>s on diff]5t p>ts ( ! disc1 t x 0 sometimes only on a c>eful projection ( diff]5t views t ,i c\ld det]m9e :at c]ta9 features ne> ! limb repres5t$4 ,b :5 ?is _h be5 done1 & ! di/ortion ?r\gh ! effect ( =e%ort5+ correct$1 ! feature 0 f\nd to be z true 9 %ape z if x _h be5 se5 9 ! c5tre ( ! planet's disc4 ,9 exam9+ ,mr4 ,dawes' draw+s x 0 necess>y t ! position ( ,m>s' axis %\ld be kn[n4 ,! data = det]m9+ ?is 7 tak5 f ,dr4 ,oudemann's det]m9ations giv5 9 a valuable pap] on ,m>s issu$ f ,mr4 ,bi%op's obs]vatory4 ,b in/ead ( calculat+ ,m>s' pres5tation by ! =mul !re giv51 ,i f\nd x conv5i5t r to make use ( geometrical con/ructions appli$ to my ',*>ts ( ! ,t]re/rial ,planets4' ,tak+ ,mdl]'s />t-po9t = ,m>tial longitudes1 t is ! longitude-l9e pass+ ne> ,dawes' =k$ bay1 ,i f\nd t my results agre$ pretty fairly ) ^? 9 ,pr(4 ,phillips' map1 s f> z ! latt] w5t2 b !re are _m details 9 my *>ts n f\nd 9 ,pr(4 ,phillips' nor 9 ,mdl]'s e>li] *>ts4 ,i h appli$ to ! diff]5t features ! names ( ^? obs]v]s :o h /udi$ ! physical peculi>ities pres5t$ by ,m>s4 ,mr4 ,dawes' "n naturally occurs m frequ5tly ?an o!rs4 ,inde$1 if ,i _h foll[$ ! rule ( giv+ to ea* feature ! "n ( its discov]]1 ,mr4 ,dawes' "n w\ld h occurr$ mu* m frequ5tly ?an x actually does4 ,on acc\nt ( ! ecc5tricity ( 8 orbit1 ,m>s is se5 mu* bett] 9 "s oppositions ?an 9 o!rs4 ,:5 be/ se5 ! s\!rn hemisph]e is br\ght m into view ?an ! nor!rn because ! summ] ( 8 nor!rn hemisph]e occurs :5 he is ne>ly 9 aphelion 7z is ! case ) ! ,e>? by ! way74 ,! relative dim5sions & pres5tation ( ,m>s1 z se5 9 opposition 9 p]ihelion1 & 9 opposition 9 aphelion1 are %[n 9 ! two r[s ( figures4 ,9 & ne> quadrature ,m>s is p]ceptibly gibb\s4 ,he is se5 ?us ab\t two mon?s be=e or aft] opposition4 ,9 ! =m] case1 he rises late & comes to ! m]idian six h\rs or s aft] midnight4 ,9 ! latt] case1 he is well se5 9 ! ev5+1 com+ to ! m]idian at six4 ,8 appe>ance & relative dim5sions z he passes f opposition to quadrature are %[n 9 ! la/ ?ree figures ( ! upp] r[4 ,m>s' pol> caps may be se5 ) v mod]ate p[]s4 ,i add f\r sets ( m]idians 7,plate #f71 by fill+ 9 :i* f ! *>ts ! obs]v] may obta9 any numb] ( views ( ! planet z x appe>s at diff]5t times4 ,pass+ ov] ! a/]oids1 :i* are n v int]e/+ objects to ! amateur telescopi/1 we come to ,jupit]1 ! giant ( ! sol> sy/em1 surpass+ our ,e>? m ?an #adjj times 9 volume1 & ov]weigh+ all ! planets tak5 toge!r twice ov]4 ,jupit] is "o ( ! easie/ ( all objects ( telescopic obs]vation4 ,no "o c mi/ake ?is orb :5 x %9es on a d>k sky1 & only ,v5us c be mi/ak5 = x :5 se5 z a morn+ or ev5+ />4 ,sometimes bo? are se5 toge!r on ! twilight sky1 & !n ,v5us is g5]ally ! bright]4 ,se51 h[ev]1 at h] brighte/ & at h] greate/ elongation f ! sun1 h] spl5d\r sc>cely exce$s t ) :i* ,jupit] %9es :5 high above ! s\!rn horizon at midnight4 ,jupit]'s satellites may be se5 ) v l[ p[]s2 inde$ ! out] ones h be5 se5 ) ! nak$ eye1 & all are visible 9 a good op]a-glass4 ,_! dim5sions relatively to ! disc are %[n 9 ,plate #g4 ,_! greate/ elongations are comp>$ ) ! disc 9 ! l[-p[] view4 ,jupit]'s belts may also be well se5 ) mod]ate telescopic p[]4 ,! out] p>ts ( 8 disc are p]ceptibly less bright ?an ! c5tre4 ,m difficult ( obs]vation are ! transits ( ! satellites & ( _! %ad[s4 ,/ill ! att5tive obs]v] c see ! %ad[s ) an ap]ture ( two in*es1 & ! satellites !mselves ) an ap]ture ( ?ree in*es4 ,! m9ute at :i* ! satellites ent] on ! disc1 or pass (f1 is giv5 9 ',dietri*s5's ,almanac4' ,! ',nautical ,almanac' also gives ! correspond+ data = ! %ad[s4 ,! eclipses ( ! satellites 9 ,jupit]'s %ad[1 & _! occultations by 8 disc1 are also giv5 9 ',dietri*s5's ,almanac4' ,9 ! inv]t+ telescope ! satellites move f "r to left 9 ! ne>] p>ts ( _! orbit1 & !re=e transit ,jupit]'s disc 9 t direction1 & f left to "r 9 ! f>!r p>ts4 ,also note t be=e opposition1 7i47 ! %ad[s travel 9 front ( ! satellites 9 transit+ ! disc2 7ii47 ! satellites are eclips$ 9 ,jupit]'s %ad[2 7iii47 !y reappe> f beh9d 8 disc4 ,on ! o!r h&1 aft] opposition1 7i47 ! %ad[s travel beh9d ! satellites 9 transit+ ! disc2 7ii47 ! satellites are occult$ by ! disc2 7iii47 !y reappe> f eclipse 9 ,jupit]'s %ad[4 ,conjunctions ( ! satellites are common ph5om5a1 & may be wait$ = by ! obs]v] :o sees ! *ance4 ,an eclipse ( "o satellite by ! %ad[ ( ano!r is n a common ph5om5on2 9 fact1 ,i h nev] he>d ( su* an eclipse be+ se54 ,t a satellite %\ld be q ext+ui%$ by ano!r's %ad[ is a ph5om5on n absolutely impossible1 b :i* _c happ5 save at long int]vals4 ,! %ad[s are n black spots z is errone\sly /at$ 9 ne>ly all popul> works on a/ronomy4 ,! %ad[ ( ! f\r?1 = in/ance1 is ne>ly all p5umbra1 ! really black "p be+ q m9ute by comp>ison4 ,! %ad[ ( ! ?ird has a consid]able p5umbra1 & ev5 t ( ! fir/ is n :olly black4 ,^! p5umbras may n be p]ceptible1 b !y affect ! appe>ance ( ! %ad[s4 ,= in/ance1 ! %ad[ ( ! f\r? is p]ceptibly l>g] b less black ?an t ( ! ?ird1 ?\gh ! ?ird is ! l>g] satellite4 ,9 transit ! fir/ satellite moves fa/e/1 ! f\r? sl[e/1 ! o!rs 9 _! ord]4 ,! %ad[ moves j z fa/ 7appreciably7 z ! satellite x belongs to4 ,sometimes ! %ad[ ( ! satellite may be se5 to ov]take 7app>5tly7 ! disc ( ano!r4 ,9 su* a case ! %ad[ does n pass ov] ! disc1 b ! disc conceals ! %ad[4 ,?is is expla9$ by ! fact t ! %ad[1 if visible ?r\gh\t its l5g?1 w\ld be a l9e rea*+ slantwise f ! satellite x belongs to1 & ! end ( ! %ad[ 7t is1 ! po9t :]e x meets ! disc7 is n ! po9t :]e ! %ad[ crosses ! orbit ( any inn] satellite4 ,?us ! latt] may be int]pos$ betwe5 ! end ( ! %ad[--! only "p ( ! %ad[ really visible--& ! eye2 b ! end ( ! %ad[ _c be int]pos$ betwe5 ! satellite & ! eye4 ,if a satellite on ! disc 7 eclips$ by ano!r satellite1 ! black spot ?us =m$ w\ld be 9 ano!r place f ! black spot on ! planet's body4 ,i m5tion all ?is because1 simple z ! "q may seem1 ,i h kn[n c>eful obs]v]s to make mi/akes on ?is subject4 ,a %ad[ is se5 cross+ ! disc & ov]tak+1 app>5tly1 a satellite 9 transit4 ,x seems !re=e1 on a fir/ view1 t ! %ad[ w hide ! satellite1 & obs]v]s h ev5 said t !y h se5 ?is happ54 ,b !y are deceiv$4 ,x is obvi\s t if "o satellite eclipse ano!r1 ! %ad[s ( bo? mu/ occupy ! same po9t on ,jupit]'s body4 ,?us x is ! ov]tak+ ( "o %ad[ by ano!r on ! disc1 & n ! ov]tak+ ( a satellite by a %ad[1 :i* det]m9es ! occurr5ce ( t z yet unrecord$ ph5om5on1 ! eclipse ( "o satellite by ano!r4#ac ,! satellites :5 f> f ,jupit] seem to lie 9 a /raight l9e ?r\gh 8 c5tre4 ,b z a matt] ( fact !y d n 9 g5]al lie 9 an exact /raight l9e4 ,if _! orbits c\ld be se5 z l9es ( light1 !y w\ld appe>1 9 g5]al1 z v long ellipses4 ,! orbit ( ! f\r? w\ld frequ5tly be se5 to be q cle> ( ,jupit]'s disc1 & ! orbit ( ! ?ird might 9 "s v exceptional in/ances pass j cle> ( ! disc4 ,! satellites move mo/ ne>ly 9 a /raight l9e 7app>5tly7 :5 ,jupit] comes to opposition 9 ! beg9n+ ( ,febru>y or ,augu/1 & !y appe> to dep>t mo/ f rectil9e> motion :5 opposition occurs 9 ! beg9n+ ( ,may & ,novemb]4 ,at ^! epo*s ! f\r? satellite may be se5 to pass above & bel[ ,jupit]'s disc at a di/ance equal to ab\t "o-six? ( ! disc's radius4 ,! %ad[s d n travel 9 ! same app>5t pa?s z ! satellites !mselves across ! disc1 b 79 an inv]t+ telescope7 bel[ f ,augu/ to ,janu>y1 & above f ,febru>y to ,july4 ,we come n[ to ! mo/ *>m+ telescopic object 9 ! heav5s--! planet ,saturn4 ,inf]ior only to ,jupit] 9 mass & volume1 ?is planet surpasses him 9 ! magnific5ce ( 8 sy/em4 ,se5 9 a telescope ( adequate p[]1 ,saturn is an object ( surpass+ lovel9ess4 ,he mu/ be an unimag9ative man :o c see ,saturn = ! fir/ "t 9 su* a telescope1 )\t a feel+ ( awe & amazem5t4 ,if !re is any object 9 ! heav5s--,i except n ev5 ! ,sun--calculat$ to impress "o ) a s5se ( ! wisdom & omnipot5ce ( ! ,creator x is ?is4 ,8 fa%ion+ h& is inde$ visible ?r\gh\t space1 b 9 ,saturn's sy/em x is mo/ impressively manife/4 ,saturn1 to be satisfactorily se51 requires a mu* m p[]ful telescope ?an ,jupit]4 ,a good #b-;in* telescope w d mu*1 h[ev]1 9 exhibit+ 8 r+s & belts4 ,i h nev] se5 him satisfactorily myself ) su* an ap]ture1 b ,mr4 ,grov] has n only se5 ! above-nam$ features1 b ev5 a p5umbra to ! %ad[ on ! r+s ) a #b-;in* telescope4 ,saturn revolv+ r\nd ! sun 9 a long p]iod--ne>ly ?irty ye>s--pres5ts sl[ly v>y+ *anges ( appe>ance 7see ,plate #g74 ,at "o "t ! edge ( 8 r+ is turn$ ne>ly t[>ds ! e>?2 sev5 or eight ye>s lat] 8 r+s are z mu* op5 z !y c ev] be2 !n !y gradually close up dur+ a correspond+ int]val2 op5 out aga91 exhibit+ a diff]5t face2 & f9ally close up z fir/ se54 ,! la/ epo* ( greate/ op5+ occurr$ 9 #ahef1 ! next occurs 9 #ahgj3 ! la/ epo* ( disappe>ance occurr$ 9 #ahfb-fc1 ! next occurs 9 #ahgi4 ,! successive views obta9$ are z 9 ,plate #g 9 ord] f "r to left1 !n back to ! "r-h& figure 7b slop$ ! o!r way72 inv]t+ ! page we h ?is figure ?us slop$1 & ! foll[+ *anges are n[ indicat$ by ! o!r figures 9 ord] back to ! fir/ 7b slop$ ! o!r way & /ill inv]t$71 ?us return+ to ! "r-h& figure z se5 )\t inv]sion4 ,! division 9 ! r+ c be se5 9 a good #b-;in* ap]ture 9 fav\rable wea!r4 ,! d>k r+ requires a good #d-;in* & good wea!r4 ,saturn's satellites d n1 l ,jupit]'s1 =m a sy/em ( ne>ly equal bodies4 ,titan1 ! six?1 is probably l>g] ?an any ( ,jupit]'s satellites4 ,! eigh? also 7,japetus7 is a l>ge body1 probably at lea/ equal to ,jupit]'s ?ird satellite4 ,b ,rhea1 ,dione1 & ,te?ys are mu* less conspicu\s1 & ! o!r ?ree _c be se5 )\t m p[]ful telescopes ?an ^? we are "h deal+ )4 ,s f> z my own exp]i5ce goes1 ,i consid] t ! five l>g] satellites may be se5 di/9ctly 9 good wea!r ) a good #c-a_/b-;in* ap]ture4 ,i h nev] se5 !m ) su* an ap]ture1 b ,i judge f ! di/9ctness ) :i* ^! satellites may be se5 ) a #d-;in* ap]ture4 ,titan is g5]ally to be look$ = at a consid]able di/ance f ,saturn--always :5 ! r+ is widely op54 ,japetus is to be look$ = yet f>!r f ! disc4 ,9 fact1 :5 ,saturn comes to opposition 9 p]ihelion 79 w9t] only ?is c happ57 ,japetus may be z f> f ,saturn z "o-?ird ( ! app>5t diamet] ( ! moon4 ,i believe t "u ^! circum/ances1 or ev5 "u less fav\rable circum/ances1 ,japetus c\ld be se5 ) a good op]a-glass4 ,s also might ,titan4 ,transits1 eclipses1 & occulations ( ,saturn's satellites c only be se5 :5 ! r+ is turn$ ne>ly edgewise t[>ds ! e>?4 ,= ! orbits ( ! sev5 inn] satellites ly+ ne>ly 9 ! plane ( ! r+s w\ld 7if visible ?r\gh\t _! ext5t7 !n only appe> z /raight l9es1 or z long ellipses cutt+ ! planet's disc4 ,! belts on ,saturn are n v conspicu\s4 ,a good #c-a_/b-;in* is requir$ 7s f> z my exp]i5ce ext5ds7 to %[ !m satisfactorily4 ,! r+s :5 turn$ edgewise ei!r t[>ds ! e>? or sun1 are n visible 9 ord9>y telescopes1 nei!r c !y be se5 :5 ! e>? & sun are on opposite sides ( ! r+s4 ,9 p[]ful telescopes ! r+s seem nev] entirely to disappe>4 ,! %ad[ ( ! planet on ! r+s may be well se5 ) a good #b-;in* telescope1 :i* w also %[ ,ball's division 9 ! r+s4 ,! %ad[ ( ! r+s on ! planet is a some:at m difficult feature4 ,! %ad[ ( ! planet on ! r+s is be/ se5 :5 ! r+s are well op5 & ! planet is 9 or ne> quadrature4 ,x is to be look$ = to ! left ( ! ball 79 an inv]t+ telescope7 at quadrature prec$+ opposition1 & to ! "r at quadrature foll[+ opposition4 ,saturn is m likely to be /udi$ at ! latt] ?an at ! =m] quadrature1 z 9 quadrature prec$+ opposition he is a morn+ />4 ,! %ad[ ( ! r+s on ! planet is be/ se5 :5 ! r+s are b mod]ately op51 & ,saturn is 9 or ne> quadrature4 ,:5 ! %ad[ lies outside ! r+s x is be/ se51 z ! d>k r+ takes (f f ! %>pness ( ! contra/ :5 ! %ad[ lies )9 ! r+4 ,x w\ld take m space ?an ,i c sp>e "h to %[ h[ x is to be det]m9$ 7indep5d5tly7 :e!r ! %ad[ lies )9 or )\t ! r+4 ,b ! ',nautical ,almanac' gives ! means ( det]m9+ ?is po9t4 ,:51 9 ! table = assign+ ! appe>ance ( ! r+s1 l is less ?an l' ! %ad[ lies outside ! r+1 :5 l is great] ?an l' ! %ad[ lies )9 ! r+4 ,uranus is j visible to ! nak$ eye :5 he is 9 opposition1 & 8 place accurately kn[n4 ,b he pres5ts no ph5om5a ( int]e/4 ,i h se5 him "u p[]s :i* made 8 disc ne>ly equal to t ( ! moon1 yet c\ld see no?+ b a fa9t blui% disc4 ,neptune also is easily f\nd if 8 place be accurately not$ on a map1 & a good f9d] us$4 ,we h only to turn ! telescope to a few />s se5 9 ! f9d] ne>ly 9 ! place m>k$ 9 our map1 & pres5tly we %all recognise ! "o we want by ! peculi>ity ( its light4 ,:at is ! l[e/ p[] :i* w exhibit ,neptune z a disc ,i d n "k1 b ,i am c]ta9 no obs]v] c mi/ake him = a fix$ /> ) a #b-;in* ap]ture & a few m9utes' pati5t scrut9y 9 fav\rable wea!r4 ,illu/ration3 ,,plate ,,vii4 ,,*apt] ,,vii4 ,,half-,,h\rs ,,) ,,! ,,sun ,,& ,,moon4 ,! moon p]haps is ! easie/ ( all objects ( telescopic obs]vation4 ,a v mod]ate telescope w %[ h] mo/ /rik+ features1 :ile ea* increase ( p[] is repaid by a view ( new details4 ,yet 9 "o s5se ! moon is a disappo9t+ object ev5 to ! possessor ( a fir/-class in/rum5t4 ,= ! mo/ c>eful & p]si/5t scrut9y1 c>ri$ on = a long s]ies ( ye>s1 too (t5 fails to rew>d ! obs]v] by any new discov]ies ( int]e/4 ,our obs]v] mu/ !re=e r be prep>$ to enjoy ! obs]vation ( recognis$ features ?an expect to add by 8 lab\rs to our k ( ! e>?'s ne>e/ neighb\r4 ,al?\gh ! moon is a pleas+ & surpris+ telescopic object :5 full1 ! mo/ int]e/+ views ( h] features are obta9$ at o!r seasons4 ,if we foll[ ! moon z %e waxes or wanes1 we see ! true nature ( t r\gh & bleak m\nta9 sc5]y1 :i* :5 ! moon is full is p>tially s(t5$ ?r\gh ! want ( %>p contra/s ( light & %ad[4 ,if we wat*1 ev5 = half an h\r only1 ! *ang+ =m ( ! ragg$ l9e sep>at+ light f d>kness on ! moon's disc1 we _c fail to be int]e/$4 ,! outly+ & isolat$ peak ( "s great m\nta9-*a9 becomes gradually l>g]1 & is f9ally m]g$ 9 ! g5]al lum9\s surface2 great circul> spaces1 enclos$ ) r\gh & rocky walls _m miles 9 diamet]1 become app>5t2 "s ) flat & p]fectly smoo? floors1 v>iegat$ ) /reaks2 o!rs 9 :i* ! flat floor is dott$ ) num]\s pits or cov]$ ) brok5 fragm5ts ( rock4 ,occasionally a regul>ly-=m$ & unusually symmetrical circul> =mation makes its appe>ance2 ! ext]ior surface ( ! wall bri/l+ ) t]races ris+ gradually f ! pla91 ! int]ior "o mu* m /eep1 & in/ead ( a flat floor1 ! inn] space is concave or cup-%ap$1 ) a solit>y peak ris+ 9 ! c5tre4 ,solit>y peaks rise f ! level pla9s & ca/ _! long n>r[ %ad[s a?w>t ! smoo? surface4 ,va/ pla9s ( a dusky t9t become visible1 n p]fectly level1 b cov]$ ) ripples1 pits1 & projections4 ,circul> wells1 :i* h no surr\nd+ wall dip bel[ ! pla91 & are met ) ev5 9 ! int]ior ( ! circul> m\nta9s & on ! tops ( _! walls4 ,f "s ( ! m\nta9s great /reams ( a brilliant :ite radiate 9 all directions & c be trac$ = hundr$s ( miles4 ,we see1 aga91 great fissures1 almo/ p]fectly /raight & ( great l5g?1 al?\gh v n>r[1 :i* appe> l ! cracks 9 moi/ clayey soil :5 dri$ by ! sun4#ad ,b int]e/+ z ^! views may be1 x 0 n = su* discov]ies z ^! t a/ronom]s exam9$ ! surface ( ! moon4 ,! exam9ation ( m]e peculi>ities ( physical condition is1 aft] all1 b b>r5 lab\r1 if x lead to no discov]y ( physical v>iation4 ,! pr9cipal *>m ( a/ronomy1 z inde$ ( all obs]vational sci5ce1 lies 9 ! /udy ( *ange--( progress1 developm5t1 & decay1 & specially ( sy/ematic v>iations tak+ place 9 regul>ly-recurr+ cycles4 ,& x is 9 ?is relation t ! moon has be5 s disappo9t+ an object ( a/ronomical obs]vation4 ,= two c5turies & a half h] face has be5 scann$ ) ! close/ possible scrut9y2 h] features h be5 portray$ 9 elaborate maps2 _m an a/ronom] has giv5 a l>ge portion ( 8 life to ! "w ( exam9+ crat]s1 pla9s1 m\nta9s1 & valleys1 = ! signs ( *ange2 b until lately no c]ta9 evid5ce--or r1 no evid5ce save ( ! mo/ d\btful "*--has be5 af=d$ t ! moon is o!r ?an a dead & useless wa/e ( ext9ct volcanoes4 ,:e!r ! exam9ation ( ! rem>kable spot call$ ,l9n--:]e lately signs 7 suppos$ to h be5 se5 ( a process ( volcanic eruption--w prove an exception to ?is rule1 rema9s to be se54 ,! evid5ce seems to me /rongly to fav\r ! supposition ( a *ange ( "s sort hav+ tak5 place 9 ?is neighb\rhood4 ,! sort ( scrut9y requir$ = ! discov]y ( *anges1 or = ! det]m9ation ( _! ext5t1 is f> too close & labori\s to be attractive to ! g5]al obs]v]4 ,yet ! k9d ( obs]vation :i* avails be/ = ! purpose is p]haps also ! mo/ int]e/+ :i* he c apply to ! lun> details4 ,! peculi>ities pres5t$ by a spot ^u ! moon are to be obs]v$ f h\r to h\r 7or f day to day1 accord+ to ! size ( ! spot7 z ! sun's light gradually sweeps across x1 until ! spot is fully light$2 !n z ! moon wanes & ! sun's light gradually passes f ! spot1 ! s]ies ( obs]vations is to be r5ew$4 ,a comp>ison ( !m is likely--especially if ! obs]v] is a good arti/ & has execut$ sev]al fai?ful del9eations ( ! region "u obs]vation1 to ?r[ mu* light ^u ! real cont\r ( ! moon's surface at ?is po9t4 ,9 ! two lun> views 9 ,plate #g "s ( ! peculi>ities ,i h describ$ are illu/rat$4 ,b ! pati5t obs]v] w easily be able to con/ruct = himself a set ( int]e/+ views ( diff]5t regions4 ,x may be notic$ t = obs]vation ( ! wan+ moon !re is no occasion to wait = ^? h\rs 9 :i* only ! wan+ moon is visible dur+ ! night4 ,( c\rse = ! obs]vation ( a p>ticul> region "u a p>ticul> illum9ation1 ! obs]v] has no *oice z to h\r4 ,b = g5]ally int]e/+ obs]vations ( ! wan+ moon he c wait till morn+ & obs]ve by daylight4 ,! moon is1 ( c\rse1 v easily f\nd by ! unaid$ eye 79 ! day "t7 :5 n v ne> to ! sun2 & ! me?ods describ$ 9 ,*apt] ,v4 w enable ! obs]v] to f9d ! moon :5 %e is s ne> to ! sun z to pres5t ! n>r[e/ possible sickle ( light4 ,"o ( ! mo/ int]e/+ features ( ! moon1 :5 %e is obs]v$ ) a good telescope1 is ! v>iety ( col\r pres5t$ by diff]5t p>ts ( h] surface4 ,we see regions ( ! pure/ :ite--regions :i* "o w\ld be apt to speak ( z sn[-cov]$1 if "o c\ld conceive ! possibility t sn[ %\ld h fall5 :]e 7n[1 at lea/7 !re is nei!r air nor wat]4 ,!n !re are ! s-call$ seas1 l>ge grey or neutral-t9t$ regions1 diff]+ f ! =m] n m]ely 9 col\r & 9 tone1 b 9 ! photographic quality ( ! light !y reflect t[>ds ! e>?4 ,"s ( ! seas exhibit a gre5i% t9t1 z ! ,sea ( ,s]5ity & ! ,sea ( ,hum\rs4 ,:]e !re is a c5tral m\nta9 )9 a circul> depression1 ! surr\nd+ pla9 is g5]ally ( a blui% /eel-grey col\r4 ,!re is a region call$ ! ,m>% ( ,sleep1 :i* exhibits a pale r$ t9t1 a col\r se5 also ne> ! ,hyrc9ian m\nta9s1 )9 a circumvallation call$ ,li*t5burg4 ,! brighte/ portion ( ! :ole lun> disc is ,ari/>*us1 ! peaks ( :i* %9e (t5 l />s1 :5 ! m\nta9 is )9 ! unillum9$ portion ( ! moon4 ,! d>ke/ regions are ,grimaldi & ,endymion & ! great pla9 call$ ,plato by mod]n a/ronom]s--b1 by ,hevelius1 ! ,great] ,black ,lake4 ,! ,sun4--,obs]vation ( ! sun is p]haps on ! :ole ! mo/ int]e/+ "w to :i* ! possessor ( a mod]ately good telescope c apply 8 in/rum5t4 ,^? wond]ful v>ieties 9 ! appe>ance ( ! sol> surface :i* h s long p]plex$ a/ronom]s1 n only supply 9 !mselves int]e/+ subjects ( obs]vation & exam9ation1 b ga9 an enhanc$ mean+ f ! consid]ation t !y speak mean+ly to u ( ! /ructure ( an orb :i* is ! s\rce ( light & heat enjoy$ by a s]ies ( dep5d5t worlds :]e( our e>? is--9 size at lea/--a comp>atively insignificant memb]4 ,sway$ by ! attraction ( ?is giant globe1 ,jupit] & ,saturn1 ,uranus & ,neptune1 z well z ! f\r m9or planets1 & ! ho/ ( a/]oids1 sweep cont9u\sly 9 _! appo9t$ orbits1 9 ev] new b ev] safe & ord]ly relations among/ ea* o!r4 ,if ! sun's light & heat 7 lo/1 all life & "w among ! d5iz5s ( ^! orbs w\ld at once cease2 if 8 attractive en]gy 7 de/roy$1 ^! orbs w\ld cease to =m a sy/em4 ,! sun may be obs]v$ conv5i5tly 9 _m ways1 "s m suit$ to ! g5]al obs]v] :o has n "t or opportunity = sy/ematic obs]vation2 o!rs m in/ructive1 ?\gh involv+ m ( prep>ation & arrangem5t4 ,! simple/ me?od ( obs]v+ ! sun is to use ! telescope 9 ! ord9>y mann]1 protect+ ! eye by means ( d>k-gre5 or neutral-t9t$ glasses4 ,"s ( ! mo/ int]e/+ views ,i h ev] obta9$ ( ! sun1 h result$ f ! use ( ! ord9>y t]re/rial or erect+ eye-piece1 capp$ ) a d>k glass4 ,! magnify+ p[] ( su* an eye-piece is1 9 g5]al1 mu* l[] ?an t available ) a/ronomical eye-pieces4 ,b vision is v pleasant & di/9ct :5 ! sun is ?us obs]v$1 & a pati5t scrut9y reveals almo/ e feature :i* ! highe/ a/ronomical p[] applicable c\ld exhibit4 ,!n1 ow+ to ! great] numb] ( int]v5+ l5ses1 !re is n ! same necessity = great d>kness or ?ickness 9 ! col\r$ glass1 s t ! col\rs ( ! sol> features are se5 mu* m satisfactorily ?an :5 a/ronomical eye-pieces are employ$4 ,9 us+ a/ronomical eye-pieces x is conv5i5t to h a rotat+ :eel atta*$1 by :i* d>k5+ glasses ( diff]5t p[] may be br\ght into use z ! v>y+ illum9ation may require4 ,^? :o wi% to obs]ve c>efully & closely a m9ute portion ( ! sol> disc1 %\ld employ ,dawes' eye-piece3 9 ?is a metallic scre5 plac$ 9 ! focus keeps away all light b su* z passes ?r\gh a m9ute hole 9 ! diaphragm4 ,ano!r conv5i5t me?od ( dim9i%+ ! light is to use a glass prism1 light be+ p>tially reflect$ f "o ( ! ext]ior surfaces1 :ile ! refract$ portion is ?r[n out at ano!r4 ,v beautiful & int]e/+ views may be obta9$ by us+ su* a pyramidal box z is depict$ 9 fig4 #aa4 ,illu/ration3 ,fig4 #aa4 ,?is box %\ld be made ( black clo? or calico fa/5$ ov] a light framework ( wire or cane4 ,! base ( ! pyramid %\ld be cov]$ on ! inside ) a %eet ( :ite glaz$ pap]1 or ) "s o!r uni=m :ite surface4 ,capta9 ,noble1 ,i believe1 makes use ( a surface ( pla/] ( ,p>is1 smoo!d :ile wet ) plate-glass4 ,! door b c enables ! obs]v] to *ange p[] )\t remov+ ! box1 :ile l>g] doors1 d e & g f1 enable him to exam9e ! image2 a d>k clo?1 su* z photograph]s use1 be+ employ$1 if necess>y1 to keep out extrane\s light4 ,! image may also be exam9$ f )\t1 if ! bottom ( ! pyramid be =m$ ( a %eet ( cut-glass or oil$ tissue-pap]4 ,:5 mak+ use ( ! me?od j describ$1 x is v necess>y t ! telescope-tube %\ld be well balanc$4 ,a me?od by :i* ?is may be conv5i5tly accompli%$ has be5 already describ$ 9 ,*apt] ,i4 ,b1 und\bt$ly1 = ! possessor ( a mod]ately good telescope !re is no way ( view+ ! sun's features comp>able to t n[ to be describ$1 :i* has be5 sy/ematically & successfully appli$ = a long s]ies ( ye>s by ! ,rev4 ,f4 ,h[lett4 ,to use 8 own words3 ,any "o possess+ a good a*romatic ( n m ?an ?ree in*es' ap]ture1 :o has a little dext]ity ) 8 p5cil1 & a little "t at 8 disposal 7all ! bett] if x be at a some:at e>ly h\r ( ! morn+7 may by ?is me?od delib]ately & satisfactorily view1 measure1 & 7if skill suffice7 del9eate mo/ ( ^? int]e/+ & gr& sol> ph5om5a ( :i* he may h read1 or :i* he may h se5 depict$1 9 v>i\s works on physical a/ronomy4#ae ,! me?od 9 "q dep5ds on ! same prop]ty :i* is involv$ 9 ! use ( ! pyramidal box j describ$1 supplem5t$ 7:]e exact & sy/ematic obs]vation is requir$7 by ! fact t objects ly+ on or betwe5 ! l5ses ( ! eye-piece are to be se5 fai?fully project$ on ! :ite surface on :i* ! sun's image is receiv$4 ,9 place1 h[ev]1 ( a box c>ri$ ^u ! telescope-tube1 a d>k5$ room 7or true cam]a obscura7 conta9s ! receiv+ %eet4 ,a *amb] is to be select$1 hav+ a w9d[ look+ t[>ds ! s\?--a little ea/]ly1 if possible1 s z to admit ( morn+ obs]vation4 ,all w9d[s are to be completely d>k5$ save "o1 ?r\gh :i* ! telescope is direct$ t[>ds ! sun4 ,an arrangem5t is to be adopt$ = prev5t+ all light f ent]+ by ?is w9d[ except su* light z passes d[n ! tube ( ! telescope4 ,?is c readily be manag$ ) a little +5uity4 ,mr4 ,h[lett describes an excell5t me?od4 ,! foll[+1 p]haps1 w suffici5tly s]ve ! purposes ( ! g5]al obs]v]3--,a pla9 frame 7portable7 is to be con/ruct$ to fit into ! w9d[3 to ! f\r sides ( ?is frame triangul> pieces ( clo? 7imp]vi\s to light7 are to be atta*$1 _! %ape be+ su* t :5 _! adjac5t edges are sewn toge!r & ! flaps /ret*$ out1 !y =m a rectangul> pyramid ( :i* ! frame is ! base4 ,?r\gh ! v]tex ( ?is pyramid 7ne> :i*1 ( c\rse1 ! clo? flaps are n sewn toge!r7 ! telescope tube is to be pass$1 & an ela/ic cord s plac$ r\nd ! ends ( ! flaps z to prev5t any light f p5etrat+ betwe5 !m & ! telescope4 ,x w n[ be possible1 )\t di/urb+ ! scre5 7fix$ 9 ! w9d[71 to move ! telescope s z to foll[ ! sun dur+ ! "t ( obs]vation4 ,& ! same arrangem5t w s]ve = all seasons1 if s manag$ t ! ela/ic cord is n f> f ! middle ( ! telescope-tube2 = 9 ?is case ! range ( motion is small comp>$ to ! range ( ! tube's extremity4 ,a l>ge scre5 ( good draw+-pap] %\ld next be prep>$4 ,?is %\ld be /ret*$ on a light frame ( wood1 & plac$ on an easel1 ! legs ( :i* %\ld be furni%$ ) holes & pegs t ! scre5 may be set at any requir$ height1 & be br\ght squ>e to ! tube's axis4 ,a l>ge ,t-squ>e ( light wood w be useful to enable ! obs]v] to judge :e!r ! scre5 is prop]ly situat$ 9 ! la/ respect4 ,we wi% n[ to direct ! tube t[>ds ! sun1 & ?is )\t dazzl+ ! eyes z by ! ord9>y me?od4 ,?is may be done 9 two ways4 ,we may ei!r1 be=e comm5c+ "w--t is1 be=e fa/5+ our ela/ic cord s z to exclude all light--direct ! tube s t its %ad[ %all be a p]fect circle 7:5 ( c\rse x is truly direct$71 !n fa/5 ! cord & aft]w>ds we c easily keep ! sun 9 ! field by slightly %ift+ ! tube z occasion requires4 ,or 7if ! ela/ic cord has already be5 fa/5$7 we may remove ! eye-tube & %ift ! telescope-tube ab\t--! direction 9 :i* ! sun lies be+ r\ghly kn[n--until we see ! spot ( light receiv$ d[n ! telescope's axis gr[ bright] & bright] & f9ally become a spot ( sun-light4 ,if a c>d be held ne> ! focus ( ! telescope !re w be se5 9 fact an image ( ! sun4 ,! telescope be+ n[ prop]ly direct$1 ! eye-tube may be slipp$ 9 aga91 & ! sun may be kept 9 ! field z be=e4 ,!re w n[ be se5 ^u ! scre5 a picture ( ! sun v brilliant & pleas+1 b p]haps a little out ( focus4 ,! focus+ %\ld !re=e next be att5d$ to1 ! increase ( cle>ness 9 ! image be+ ! te/ ( approa* to ! true focus4 ,& aga91 x w be well to try ! effect ( slight *anges ( di/ance betwe5 ! scre5 & ! telescope's eye-piece4 ,mr4 ,h[lett consid]s "o y>d z a conv5i5t di/ance = produc+ an excell5t effect ) almo/ any eye-piece t ! /ate ( ! atmosph]e w admit (4 ,( c\rse1 ! image becomes m %>ply def9$ if we br+ ! scre5 ne>] to ! telescope1 :ile all ! details are enl>g$ :5 we move ! scre5 away4 ,! enl>gem5t has no limits save ^? dep5d+ on ! am\nt ( light 9 ! image4 ,b1 ( c\rse1 ! obs]v] mu/ n expect enl>gem5t to br+ ) x a view ( new details1 aft] a c]ta9 magnitude ( image has be5 atta9$4 ,/ill !re is some?+ in/ructive1 ,i ?9k1 9 occasionally gett+ a v magnifi$ view ( "s rem>kable spot4 ,i h (t5 look$ ) enhanc$ feel+s ( awe & wond] on ! gigantic image ( a sol> spot ?r[n by means ( ! diagonal eye-piece ^u ! ceil+ ( ! obs]v+-room4 ,blurr$ & indi/9ct ?r\gh ov]-magnify+1 yet ) a new mean+ to me1 !re ! va/ abysm lies pictur$2 vague imag9+s ( ! va/ & incompreh5sible ag5cies at "w 9 ! great c5tre ( our sy/em cr[d unbidd5 into my m9d2 & ,i seem to feel--n m]ely ?9k ab\t--! /up5d\s gr&eur ( t life-emitt+ orb4 ,to return1 h[ev]1 to obs]vation3--,by slightly %ift+ ! tube1 diff]5t p>ts ( ! sol> disc c be br\ght successively ^u ! scre5 & scrut9iz$ z readily z if !y 7 drawn ^u a *>t4 ,) a p[] (--say ab\t #fj or #hj l9e>--! mo/ m9ute sol> spot1 prop]ly s call$1 t is capable ( =mation 7,mr4 ,h[lett believes !y are nev] less ?an ?ree seconds 9 l5g? or bread?7 w be m readily detect$ ?an by any o!r me?od1 see ,plate #g2 z also w any facul1 mottl+1 or 9 %ort1 any o!r ph5om5a t may !n be exi/+ on ! disc4 ,drift+ cl\ds frequ5tly sweep by1 to v>y ! sc5e1 & occasionally an arial hail- or sn[-/orm4 ,mr4 ,h[lett has m ?an once se5 a di/ant flight ( rooks pass sl[ly across ! disc ) wond]ful di/9ctness1 :5 ! sun has be5 at a l[ altitude1 & likewise1 mu* m frequ5tly1 ! rapid da% ( />l+s1 :i*1 v mu* clos] at h&1 frequ5t 8 *ur*-t[]4 ,an eclipse ( ! sun1 or a transit ( an inf]ior planet1 is also mu* bett] se5 9 ?is way ?an by any o!r me?od ( obs]v+ ! sol> disc4 ,9 ,plate #g are pres5t$ sev]al sol> spots z !y h appe>$ to ,mr4 ,h[lett1 ) an in/rum5t ( mod]ate p[]4 ,! grotesque =ms ( "s ( ^! are rem>kable2 & ! v>iations ! spots und]go f day to day are p>ticul>ly int]e/+ to ! ?\ghtful obs]v]4 ,a me?od ( measur+ ! spots may n[ be describ$4 ,x is n likely inde$ t ! ord9>y obs]v] w c>e to ent] ^u any sy/ematic s]ies ( measurem5ts4 ,b ev5 9 8 case1 ! means ( =m+ a g5]al comp>ison betwe5 ! spots he sees at diff]5t times _c fail to be valuable4 ,also ! k--:i* a simple me?od ( measurem5t supplies--( ! actual dim5sions ( a spot 9 miles 7r\ghly7 is calculat$ to enhance our e/imate ( ! importance ( ^! features ( ! sol> disc4 ,i give ,mr4 ,h[lett's me?od 9 8 own words3-- ,cause y\r optician to rule = y on a circul> piece ( glass a numb] ( f9e graduations1 ! #bjj? "p ( an in* ap>t1 ea* fif? & t5? l9e be+ ( a diff]5t l5g? 9 ord] to assi/ ! eye 9 _! enum]ation4 ,ins]t ?is betwe5 ! ant]ior & po/]ior l5ses ( a ,huyg5ian eye-piece ( mod]ate p[]1 say #hj l9e>4 ,direct y\r telescope ^u ! sun1 & hav+ s arrang$ x t ! :ole disc ( ! sun may be project$ on ! scre51 c\nt c>efully ! numb] ( graduations t are se5 to exactly occupy ! sol> diamet]4444 ,x matt]s n 9 :i* direction y measure y\r diamet]1 provid$ only ! sun has ris5 "s #ah or #bj above ! horizon1 & s escap$ ! di/ortion occasion$ by refraction4#af ,next let u suppose t our obs]v] has be5 obs]v+ ! sun on any day ( ! ye>1 say1 if y *oose1 at ! "t ( its mean app>5t diamet]1 namely ab\t ! fir/ ( ,april or fir/ ( ,octob]1 & has asc]ta9$ t 7z is ! case ) ,mr4 ,h[lett's in/rum5t7 sixty-f\r graduations occupy ! diamet] ( ! project$ image4 ,n[ ! semi-diamet] ( ! sun1 at ! epo*s above m5tion$1 accord+ to ! tables giv5 = e day ( ! ye> 9 ! ',nautical ,almanac' 7! same z 9 ,dietri*s5 & ,hannay's v useful compilation7 is #af' #b1 & consequ5tly 8 mean total diamet] is #cb' #d or #aibd4 ,if n[ we divide #aibd by #fd ?is w1 ( c\rse1 aw>d z ne>ly z possible #cj z ! value 9 cele/ial arc ( ea* graduation1 ei!r z se5 on ! scre51 or z appli$ directly to ! sun or any heav5ly body l>ge en\gh to be measur$ by x4 ,s9ce ! sun's diamet] is ab\t #hej1jjj miles1 ea* graduation 79 ! case above specifi$7 corresponds to "o-#fd? "p ( #hej1jjj miles--t is1 to a l5g? ( #ac1bef miles on ! sun's surface4 ,any o!r case c be treat$ 9 precisely ! same mann]4 ,x w be f\nd easy s to place ! scre5 t ! di/ance betwe5 successive graduations 7z se5 project$ ^u ! scre57 may correspond to any desir$ unit ( l9e> measurem5t--say an in*4 ,!n if ! obs]v] use transp>5t trac+-pap] rul$ ) fa9t l9es =m+ squ>es half-an-in* 9 size1 he c com=tably copy directly f ! scre5 any sol> ph5om5a he may be /ruck )4 ,a v>iety ( me?ods ( draw+ w sugge/ !mselves4 ,mr4 ,h[lett1 9 ! pap] ,i h quot$ f above1 describes a v satisfactory me?od1 :i* ^? :o are anxi\s to devote !mselves s]i\sly to sol> obs]vation w d well to /udy4 ,x is necess>y t ! obs]v] %\ld be able to det]m9e approximately :]e ! sun's equator is situat$ at ! "t ( any obs]vation1 9 ord] t he may assign to any spot or set ( spots its true position 9 relation to sol> longitude & latitude4 ,mr4 ,h[lett %[s h[ ?is may be done by ?ree obs]vations ( ! sun made at any fix$ h\r on successive days4 ,p]haps ! foll[+ me?od w s]ve ! purpose ( ! g5]al obs]v] suffici5tly well3-- ,! h\r at :i* ! sun crosses ! m]idian mu/ be tak5 = ! special obs]vation n[ to be describ$4 ,?is h\r c always be le>nt f ',dietri*s5's ,almanac'2 b noon1 civil "t1 is ne> en\gh = practical purposes4 ,n[ x is necess>y fir/ to "k ! position ( ! ecliptic ) ref]5ce to ! cele/ial equator4 ,( c\rse1 at noon a horizontal l9e across ! sun's disc is p>allel to ! equator1 b ! position ( t diamet] ( ! sun :i* co9cides ) ! ecliptic is n con/ant3 at ! summ] & w9t] sol/ices ?is diamet] co9cides ) ! o!r1 or is horizontal at noon2 at ! spr+ equ9ox ! sun 7:i* travels on ! ecliptic7 is pass+ t[>ds ! nor? ( ! equator1 cross+ t curve at an angle ( #bc-a_/b1 s t ! ecliptic co9cides ) t diamet] ( ! sun :i* cuts ! horizontal "o at an angle ( #bc-a_/b & has its left end above ! horizontal diamet]2 & at ! autumn equ9ox ! sun is desc5d+ & ! same description applies1 only t ! diamet] 7incl9$ #bc-a_/b to ! horizon7 :i* has its "r end upp]mo/1 n[ repres5ts ! ecliptic4 ,= int]m$iate dates1 use ! foll[+ little table3-- ---------------------------------------- ---------------------------------- ,date4 ,dec4 #bb;,jan4 #e;,jan4 #bj;,feb4 #d;,feb4 #ai,m>4 #e ,m>4 #ba 7,circit]47 ,june #f,may #ba ,may #e ,apr4 #bj;,apr4 #e ---------------------------------------- --------------------------- ,incl9ation ( ,left ,left ,left ,left ,left ,left ,left ,ecliptical ,diamet] ( ,sun to ! #j #j' #fbd' #abad' #agc' #bjcf' #bbdd' #bcbg' ,horizon4#ag ,"r ,"r ,"r ,"r ,"r ,"r ,"r ---------------------------------------- --------------------------- ,date4 ,dec4 #g,nov4 #bb,nov4 #g,oct4 #bc,oct4 #h 7,circit]47 ,jan4 #ba;,july #g;,july #bc;,aug4 #f;,aug4 #bc,sept4 #g,sept4 #bc ---------------------------------------- ---------------------------------- ,n[ if our obs]v] describe a circle1 & draw a diamet] incl9$ accord+ to above table1 ?is diamet] w\ld repres5t ! sun's equator if ! axis ( ! sun 7 squ>e to ! ecliptic-plane4 ,b ?is axis is slightly incl9$1 ! effect ( :i* is1 t on or ab\t ,june #aj ! sun is situat$ z %[n 9 fig4 #ad ) respect to ! ecliptic ab2 on or ab\t ,septemb] #aa he is situat$ z %[n 9 fig4 #ac2 on or ab\t ,decemb] #aa z %[n 9 fig4 #ab2 & on or ab\t ,m>* #aj z %[n 9 fig4 #ae4 ,! incl9ation ( 8 equator to ! ecliptic be+ s small1 ! /ud5t c f9d little difficulty 9 det]m9+ ) suffici5t approximation ! relation ( ! sun's pol> axis to ! ecliptic on int]m$iate days1 s9ce ! equator is nev] m incl9$ ?an 9 figs4 #ab & #ad1 nev] m op5$ out ?an 9 figs4 #ac & #ae4 ,hav+ !n drawn a l9e to repres5t ! sun's ecliptical diamet] incl9$ to ! horizontal diamet] z above describ$1 & hav+ 7) ?is l9e to correspond to ab 9 figs4 #ab-ae7 drawn 9 ! sun's equator suitably incl9$ & op5$ out1 he has ! sun's actual pres5tation 7at noon7 z se5 ) an erect+ eye-piece4 ,hold+ 8 picture upside d[n1 he has ! sun's pres5tation z se5 ) an a/ronomical eye-piece--&1 f9ally1 look+ at 8 picture f beh9d 7)\t inv]t+ x71 he has ! pres5tation se5 :5 ! sun is project$ on ! scre54 ,h5ce1 if he make a copy ( ?is la/ view ( 8 diagram ^u ! c5tre ( 8 scre51 & us+ a l[ p[]1 br+ ! :ole ( ! sun's image to co9cide ) ! circle ?us drawn 7to a suitable scale7 on ! scre51 he w at once see :at is ! true position ( ! diff]5t sun-spots4 ,aft] a little practice ! con/ruction ( a suitably siz$ & m>k$ circle on ! scre5 w n occupy m ?an a m9ute or two4 ,illu/ration3 ,fig4 #ab4 ,illu/ration3 ,fig4 #ac4 ,illu/ration3 ,fig4 #ad4 ,illu/ration3 ,fig4 #ae4 ,x mu/ be notic$ t ! sun's app>5t diamet] is n always ! same4 ,he is ne>] to u 9 w9t] ?an 9 summ]1 &1 ( c\rse1 8 app>5t diamet] is great] at ! =m] ?an at ! latt] season4 ,! v>iation ( ! app>5t diamet] corresponds 7inv]sely7 to ! v>iation ( di/ance4 ,z ! sun's greate/ di/ance f ! e>? is #ic1jjj1jjj miles 7pretty ne>ly7 & 8 lea/ #ij1jjj1jjj1 8 greate/1 mean1 & lea/ app>5t diamet]s are z #ic1 #ia-a_/b1 & #ij respectively2 t is1 z #fb1 #fa1 & #fj respectively4 ,mr4 ,h[lett consid]s t ) a good #c-;in* telescope1 appli$ 9 ! mann] we h describ$1 all ! sol> features may be se51 except ! sep>ate granules disclos$ by fir/-class in/rum5ts 9 ! h&s ( su* obs]v]s z ,dawes1 ,hugg9s1 or ,sec*i4 ,facul may1 ( c\rse1 be well se54 ,!y are to be look$ = ne> spots :i* lie close to ! sun's limb4 ,:5 ! sun's g5]al surface is c>efully scrut9is$1 x is f\nd to pres5t a mottl$ appe>ance4 ,?is is a some:at delicate feature4 ,x results1 und\bt$ly1 f ! comb9$ effect ( ! granules sep>ately se5 9 p[]ful in/rum5ts4 ,sir ,john ,h]s*el has /at$ t he _c recognise ! m>bl$ appe>ance ( ! sun ) an a*romatic4 ,mr4 ,webb1 h[ev]1 has se5 ?is appe>ance ) su* a telescope1 ( mod]ate p[]1 us$ ) direct vision2 & c]ta9ly ,i c corroborate ,mr4 ,h[lett 9 ! /atem5t t ?is appe>ance may be mo/ di/9ctly se5 :5 ! image ( ! sun is receiv$ )9 a well-d>k5$ room4 ,my space w n p]mit me to ent] "h ^u ! discussion ( any ( ^? int]e/+ speculations :i* h be5 broa*$ conc]n+ sol> ph5om5a4 ,we may hope t ! great eclipse ( ,augu/1 #ahfh1 :i* promises to be ! mo/ fav\rable 7= effective obs]vation7 t has ev] tak5 place1 w af=d a/ronom]s ! opportunity ( resolv+ "s important que/ions4 ,x seems z if we 7 on ! v]ge ( great discov]ies1--& c]ta9ly1 if p]sev]+ & well-direct$ lab\r w\ld seem 9 any case to r5d] su* discov]ies due z man's j rew>d1 we may well say t he des]ves %ortly to reap a h>ve/ ( exact k respect+ sol> ph5om5a4 ,,! ,,end4 ,,footnotes3 ,footnote #a3 ,su* a telescope is mo/ p[]ful ) ! %orte/ sight4 ,x may be rem>k$ t ! use ( a telescope (t5 reveals a diff]5ce 9 ! sight ( ! two eyes4 ,9 my own case1 = in/ance1 ,i h f\nd t ! left eye is v %ort-sight$1 ! sight ( ! "r eye be+ ( ab\t ! av]age range4 ,accord+ly ) my left eye a #e-a_/b-;foot object-glass1 alone1 =ms an effective telescope1 ) :i* ,i c see ,jupit]'s moons q di/9ctly1 & "u fav\rable circum/ances ev5 ,saturn's r+s4 ,i f9d t ! full moon is too bright to be obs]v$ 9 ?is way )\t pa91 except at l[ altitudes4 ,footnote #b3 ,betelgeuse--commonly int]pret$ ! ,giant's ,%\ld]--ibt-al-jauza4 ,! words1 h[ev]1 really signify1 ! armpit ( ! c5tral "o1 ,orion be+ s nam$ because he is divid$ c5trally by ! equator4 ,footnote #c3 ,i h nev] be5 able to see m ?an f\r ) a #c-c_/d-;in* ap]ture4 ,i give a view ( ! trapezium z se5 ) an #h-;in* equatorial4 ,footnote #d3 ,sir ,w4 ,h]s*el sev]al times saw epsilon ,lyr z a d\ble4 ,bessel also relates t :5 he 0 a lad ( ?irte5 he c\ld see ?is /> d\ble4 ,i ?9k p]sons hav+ av]age eye-sight c\ld see x d\ble if !y select$ a suitable h\r = obs]vation4 ,my own eye-sight is n good en\gh = ?is1 b ,i c di/9ctly see ?is /> w$g$ :5ev] ! l9e jo9+ ! compon5ts is incl9$ ab\t #de to ! horizon1 & also :5 ,lyra is ne> ! z5i?4 ,footnote #e3 ,!y 7 s describ$ by ,admiral ,smy? 9 #ahci4 ,mr4 ,ma91 9 #ahfb1 describes !m z /raw-col\r$ & r$di%1 :ile ,mr4 ,webb1 9 #ahfe1 saw !m pale-yell[ & lilac6 ,footnote #f3 ,or ! obs]v] may sweep f omicron t[>ds nu1 look+ = ,r ab\t two-fif?s ( ! way f omicron to nu4 ,footnote #g3 ,"h a s+le p]iod only is tak51 to get back to a conv5i5t h\r ( ! ev5+4 ,footnote #h3 ,"h a s+le p]iod only is tak51 to get back to a conv5i5t h\r ( ! ev5+4 ,footnote #i3 ,i h con/ruct$ a zodiac-*>t1 :i* w enable ! /ud5t to m>k 9 ! pa? ( a planet1 at any season ( ! ye>1 f ! record$ places 9 ! almanacs4 ,footnote #aj3 ,x is conv5i5t to rememb] t ?r\gh precession a /> ne> ! ecliptic %ifts z respects ! ,r4,a4 & ,dec4 l9es1 ?r\gh an arc ( "o degree--or ne>ly twice ! moon's diamet]--9 ab\t #gb ye>s1 all o!r />s ?r\gh a less arc4 ,footnote #aa3 ,m]cury is be/ se5 :5 9 quadrature to ! sun1 b n 7z ,i h se5 /at$7 at ^? quadratures 9 :i* he atta9s 8 maximum elongation f ! sun4 ,?is w appe> s+ul>1 because ! maximum elongation is ab\t #bg1 ! m9imum only ab\t #ah4 ,b x happ5s t 9 our nor!rn latitudes ,m]cury is always s\? ( ! sun :5 he atta9s 8 maximum elongation1 & ?is fact ex]cises a m important effect ?an ! m]e am\nt ( elongation4 ,footnote #ab3 ,x does n seem to me t ! difficulty ( detect+ ,m]cury is due to ! difficulty ( id5tify+ x among/ ! surr\nd+ />s1 dur+ ! %ort "t t x c be se5 7,h9d's ',introduction to ,a/ronomy'74 ,!re are few />s :i* are comp>able ) ,m]cury 9 brilliancy1 :5 se5 "u ! same light4 ,footnote #ac3 ,i may notice ano!r error sometimes made4 ,x is said t ! %ad[ ( a satellite appe>s elliptical :5 ne> ! edge ( ! disc4 ,! %ad[ is 9 reality elliptical :5 ?us situat$1 b appe>s circul>4 ,a mom5t's consid]ation w %[ t ?is %\ld be s4 ,! "p ( ! disc conceal$ by a satellite ne> ! limb is also elliptical1 b ( c\rse appe>s r\nd4 ,footnote #ad3 ,f a pap] by ,mr4 ,bre51 9 ! ',popul> ,sci5ce ,review1' ,octob]1 #ahfd4 ,footnote #ae3 ',intellectual ,obs]v]' = ,july1 #ahfg1 to :i* magaz9e ! read] is ref]r$ = full details ( ,mr4 ,h[lett's me?od ( obs]vation1 & = illu/rations ( ! appliances he made use (1 & ( "s ( 8 results4 ,footnote #af3 ,z ! sun does n atta9 su* an altitude z #ah dur+ two mon?s 9 ! ye>1 x is well to notice t ! true l5g? ( ! sun's app>5t sol> diamet] is det]m9able ev5 imm$iately aft] sun-rise1 if ! l9e ( graduation is made to co9cide ) ! horizontal diamet] ( ! picture on ! scre5--= refraction does n affect ! l5g? ( ?is diamet]4 ,footnote #ag3 ,! words ,left & ,"r indicate :i* end ( ! sun's ecliptical diamet] is upp]mo/ at ! dates 9 upp] or l[] r[ respectively4 ,,london3 ,,pr9t$ ,,by ,w4 ,,cl[es ,,& ,,sons1 ,,duke ,,/reet1 ,,/am=d ,,/reet1 ,,& ,,*>+ ,,cross4