,illu/ration3 ,frontispiece--,,build+   
,,& ,,dome ,,f ,,s\?                    
,,dep>tm5t ,,( ,,! ,,int]ior      ,hon4 
,*>les ,/ew>t           ,m9i/]    ,w4   
,w4 ,cory1 ,c4,m4,g4      ,deputy ,m9i/]
        ,!    ,dom9ion ,a/rophysical    
,obs]vatory      ,victoria1 ,b4,c4      
,a sket* ( ! developm5t ( a/ronomy    9 
,canada & ( ! f\nd+ ( ?is obs]vatory4   
,a description ( ! build+ & ( !         
me*anical & optical details ( !         
telescope4 ,an    acc\nt ( ! pr9cipal "w
 ( ! in/itution4      ,by    ,j4 ,s4    
,plaskett1 ,f4,r4,s4        ,ottawa     
,f4 ,a4 ,,acl&1    ,pr9t] to ! ,k+'s    
,mo/ ,excell5t ,maje/y    #aibc         
,,/aff ,,( ,,! ,,obs]vatory3            
,director              ,j4 ,s4          
,plaskett1 ,b4,a41 ,d4,sc41             
,f4,r4,s4,c41 ,f4,r4,s4    ,rese>*      
,a/ronom]                               
,w4 ,e4 ,h>p]1 ,m4,a4    ,a/ronom]      
,reynold ,k4 ,"y1 ,ph4,d41 ,f4,r4,s4,c4 
,a/ronom]                               
,h4 ,h4 ,plaskett1 ,b4,a4    ,secret>y  

,miss ,h4 ,r4 ,keay    ,obs]v+ ,assi/ant
                           ,t4 ,t4      
,hut*ison1 ,esq4          ,,! ,,dom9ion 
,,a/rophysical ,,obs]vatory             
,,victoria1 ,b4,c4    ,by ,j4 ,s4       
,,plaskett1 ,director4                  
,,section #a4--;,,hi/ory ,,&            
,,con/ruction      ,introduction    ,?is
 description ( ! obs]vatory1 its        
equipm5t & "w has be5  writt5 by !      
director 9 response to a ne$1 frequ5tly 
express$  by ! num]\s visitors to !     
in/itution1 ( a non-te*nical  acc\nt ( !
 pr9ciples ( ! telescope & ( ! "w ( !   
in/itution4 ,?is acc\nt w comm5ce by a  
%ort hi/orical sket*  ( ! beg9n+s ( !   
und]tak+ foll[$ by a description ( !    
obs]vatory & telescope & conclud$ by a  
resume ( its "w4      ,hi/orical ,sket* 
,?is obs]vatory is a bran* ( ! ,dep>tm5t
 ( ! ,int]ior  ( ! ,f$]al ,gov]nm5t1 !  
dep>tm5t :i* has *>ge (  ! adm9i/ration 
( ! we/]n l&s ( ! ,dom9ion4 ,9 !        
colonization ( ^! l&s1 "o ( ! obvi\s    
fir/ ne$s 0 a  survey ( ! b\nd>ies &    

subdivision into t[n%ips & sections4    
,?is ne$ l$ to ! organization ( a       
surveys bran* ( ! dep>tm5t  & out ( !   
necessity ( accurate a/ronomical        
obs]vations to  delimit ! b\nd>ies &    
def9e ! position ( ! base l9es  =       
subdivision "w arose ! a/ronomical      
bran*4 ,! fir/ ,*ief  ,a/ronom] (       
,canada1 ! late ,dr4 ,w4 ,f4 ,k+1 0 a   
man ( /]l+  integrity & rem>kable       
ability & to 8 g5ius mu/ be ascrib$ 9   
l>ge degree ! pres5t developm5t (       
a/ronomy 9 ,canada4 ,z ,*ief  ,a/ronom] 
& ,h4 ,m4 ,commission] ( ,int]national  
,b\nd>ies1 he  e>ly realiz$ ! ne$ ( an  
obs]vatory = an initial m]idian1 =  h\s+
 & /&>diz+ ! in/rum5ts1 & = "s          
a/ronomical  rese>*4 ,he 0 successful 9 
hav+ ! f9e ,dom9ion ,obs]vatory  erect$ 
on ! ,exp]im5tal ,f>m1 ,ottawa1 9 #aije 
:i* h\s$ !  ,a/ronomical ,bran*1 ! /aff 
( ! ,int]national ,b\nd>y ,surveys  &   
lat] ! ,geodetic ,survey ( ,canada1 (   
:i* he 0 ! fir/  sup]9t5d5t4    ,!      
,dom9ion ,obs]vatory 0 equipp$ ) a      

#ae-;in* refractor  provid$ ) micromet]1
 photomet]1 sol> & /ell> cam]as1  &     
spectrograph4 ,! writ] 0 entru/$ ) ! "w 
) ?is  telescope & ! spectroscopic "w   
especially 0 en]getically  develop$ &   
help$1 ) ! o!r activities ( !           
in/itution1 to  br+ gratify+ recognition
 f ! sci5tific _w4 ,! ne$ ( a  l>g]     
ap]ture = ext5d+ ?is "p ( ! "w 0 soon   
realiz$  by ! writ] & 0 br\ght to !     
att5tion ( ! ,gov]nm5t4  ,aft] "s       
delays1 ow+ to v>i\s circum/ances1 x 0  
f9ally  decid$ e>ly 9 #aiac to provide a
 l>ge reflector = ext5d+  ! "w4         
,enquiries 7 at once made1              
specifications prep>$ &  e/imates obta9$
 f prospective mak]s ( ! in/rum5t4      
,contracts  7 f9ally aw>d$ 9 ,octob]    
#aiac to ! ,john ,a4 ,bra%e> ,co4 (     
,pittsburgh = ! optical p>ts & to !     
,w>n]  ,swasey ,co4 (  ,clevel& = !     
me*anical p>ts ( a #gb-;in* reflect+    
telescope4      ,location    ,x 0       
necess>y to "k ! location ( ! in/rum5t  
be=e !  design ( ! m\nt+ c\ld be        

complet$ z ! angle ( ! pol>  axis dep5ds
 ^u ! latitude ( ! site4 ,:5 ! new      
telescope  0 fir/ propos$ !re 0 no ?\ght
 ( locat+ else:]e ?an at  ! seat (      
gov]nm5t at ,ottawa4 ,h[ev]1 ^u fur!r   
consid]ation  x 0 decid$ t ! telescope  
%\ld be locat$ :]e1 9 ,canada1  ! be/   
obs]v+ conditions prevail$4 ,to det]m9e 
?is location  prelim9>y selection ( five
 likely /ations 0 made by ! aid (  ,sir 
,fr$]ic ,/up>t1 *ief ( ! ,meteorological
 ,s]vice f !  meteorological records4   
,^! /ations1 at ,ottawa1 at ,m$ic9e     
,hat1  at ,banff1 at ,p5ticton1 & at    
,victoria 7 occupi$ by ,mr4 ,w4 ,e4     
,h>p]1 a/ronom] at ,ottawa & !          
a/ronomical conditions 7  obs]v$ by     
means ( a #d4e-;in* telescope4 ,victoria
 0 unmi/akably  sup]ior 9 8see+0 or     
def9+ p[]1 9 l[ diurnal & seasonal      
range ( temp]ature & ab\t equal s f> z  
quantity ( cle> sky is  conc]n$4 ,= su* 
a l>ge telescope z a #gb-;in* !re c\ld  
be no  "q ( ! m>k$ a/ronomical          
advantages ( su* a location1 &  x 0     

!re=e decid$ to locate ! telescope at   
,victoria4 ,:ile !  obs]vatory %\ld n be
 9 ! city itself x %\ld n be too f>     
away1 n only on acc\nt ( accessibility &
 facility 9 obta9+  supplies1 b also !  
advantage\s conditions ( good see+1 l[  
diurnal range ( temp]ature & small      
ra9fall 7 conf9$ to a  relatively small 
area ne> ,victoria4 ,an isolat$         
monadnock call$  locally ,little ,saani*
 ,m\nta9 b n[ nam$ ,obs]vatory ,hill1 0 
select$4 ,?is hill is ab\t #g miles nor?
 ( ,victoria & has a ma9  road & an     
int]urban railway pass+ its base4 ,x has
 an elevation (  #gcj feet1 suffici5t   
area ar\nd ! summit = all necess>y      
build+s  & 0 by f> ! mo/ suitable site  
available4      ,con/ruction    ,!      
,prov9cial ,gov]nm5t _h g5]\sly agre$ to
 give #aj1jjj = !  pur*ase ( a site & to
 build a road to ! summit4 ,?is und]tak+
  0 fully met & ! road1 spl5didly locat$
 & con/ruct$ &  co/+ ov] #be1jjj1 0     
complet$ 9 ! spr+ ( #aiae4 ,contracts  =
 ! con/ruction ( ! telescope pi] & !    

circul> /eel  walls ( ! build+ 7 aw>d$  
to a local firm & ?is "w  0 complet$ 9  
#aiaf4 ,! revolv+ dome ) accessories = !
  op]ation ( ! telescope 0 made by !    
,w>n]  ,swasey ,co41 !  build]s ( !     
telescope m\nt+1 & 0 complet$ & erect$ 9
  #aiaf1 ?us mak+ ! build+ ready = !    
telescope4    ,! design ( ! m\nt+ 0 v   
c>efully gone into by ! ,w>n]   ,swasey 
,co4 9 collaboration ) ! writ] & 0      
complet$ 9 !  autumn ( #aiad4           
,con/ruction 0 at once begun & ! m\nt+ 0
  complet$ & tempor>ily erect$ at       
,clevel& 9 ,may #aiaf4 ,x 0 !n  %ipp$ to
 ,victoria & p]man5tly erect$ 9 its     
build+ by ,novemb]  #aiaf4    ,! ord] = 
! l>ge disc = ! #gb-;in* mirror & = an  
auxili>y flat ( #ee in*es diamet] = te/+
 ! #gb-;in* 0 giv5  to ! ,/4 ,goba9     
,glass ,works ( ,p>is by ! ,jno4 ,a4    
,bra%e> ,co4  z soon z ! contract 0     
aw>d$4 ,! #gb-;in* disc 0 ca/ &  anneal$
 by ,june #aiad & 0 =tunately %ipp$ at  
once )\t  wait+ = ! #ee-;in* disc4 ,x   
left ,antw]p only ab\t a week be=e  w> 0

 decl>$ & x 0 only by ?is small m>g9 t  
,canada n[  has a #gb-;in* telescope4   
,gr9d+ & poli%+ 7 at once begun  b !    
lack ( ! l>ge flat & o!r difficulties   
delay$ !  completion & x 0 n until      
,april #aiah1 ab\t a ye> & a half  aft] 
! completion ( ! m\nt+1 t ! figur+ 0    
f9ally  complet$ & ! telescope ready =  
"w4 ,nev]!less1 = an  und]tak+ ( su*    
magnitude ! "w 0 complet$ 9 record "t1  
f\r & a half ye>s aft] ! aw>d+ ( !      
contracts4          ,,section #b4--,,!  
,,build+ ,,& ,,dome      ,! ,obs]vatory 
,build+    ,! build+ = h\s+ a l>ge      
reflect+ telescope requires to  be (    
special design = ! be/ results4 ,x %\ld 
n rise above  ! %ade temp]ature dur+ !  
day & %\ld rapidly assume &  foll[ !    
ext]nal temp]ature at night4 ,su*       
mat]ials z brick or  /one are obvi\sly n
 suitable & all rec5t telescope build+s 
are entirely ( metallic con/ruction 9   
ord] to assume quickly !  night         
temp]ature1 & ( d\ble-wall$1 v5tilat$   
type to prev5t  ov]heat+ f ! sun's rays4

 ,! build+ = ! #gb-;in* telescope  is   
entirely ( /eel con/ruction1 circul> 9  
=m1 #ff feet 9  ext]nal diamet] & )     
v]tical walls #cb feet high4 ,a view f  
! s\? is giv5 9 ! ,frontispiece & f !   
nor? 9 ,fig4 #a1  %[+ ! city ( ,victoria
 & ! /raits ( ,juan de ,fuca 9 !        
backgr\nd4 ,an ext]nal & int]nal cov]+ (
 galvaniz$ iron  sep>at$ by ab\t #af    
in*es all[s free circulation ( air f a  
p]iph]al op5+ at ! base up ?r\gh a      
simil> d\ble wall$ dome  & out ( l\vres 
at ! top4 ,! gr\nd floor ( ,t]razo is   
laid  directly on ! rock base & ! obs]v+
 floor #bb feet above ?is  is =m$ ( /eel
 gird]s & *eck]$ /eel plate4 ,9 ! c5tre 
(  ! gr\nd floor rises ! massive pi] to 
support ! telescope1 (  re9=c$ concrete 
& symmetrical tap]+ =m4 ,! pi] is       
actually  d\ble1 unit$ bel[ ! obs]v+    
floor by a massive re9=c$ ar*  & ext5d+ 
above ! floor z two pi]s 7see ,fig4 #b7 
"o = ea*  end ( ! pol> axis4 ,tempor>y  
p>titions on ! gr\nd floor provide  a   
d>k room1 sleep+ room1 & tempor>y (fice 

qu>t]s4    ,illu/ration3 ,fig4          
#a4--,,obs]vatory ,,build+ ,,f ,,!      
,,nor?      ,! ,dome    ,?is circul>    
/eel build+ is capp$ by a circul> plate 
support$ by  massive gird]s on :i* is   
plac$ a curv$ railroad iron rail turn$  
& adju/$ p]fectly level & circul>4 ,!   
hemisph]ical dome turns  on ?is rail on 
#bd massive :eels m\nt$ on roll] be>+s &
 is  rotat$ by an electric motor        
me*anism op]at$ by rev]s+ swit*es  on   
ea* side ( ! s\? pi]4 ,! framework ( ?is
 dome1 :i* is  #ff feet 9 ext]nal       
diamet] & ab\t #ch feet high1 ! l[] #e  
feet  be+ cyl9drical1 consi/s ess5tially
 ( a circul> base to :i*  ! be>+ :eels  
are atta*$ & two d\ble1 v deep & rigid  
ma9 ribs1 "o ( :i* c be se5 9 ,fig4 #c1 
#af feet ap>t 9 !  cle> & ext5d+ p>allel
 to ea* o!r entirely across ! dome4  ,^!
 are unit$ #f feet beyond ! z5i? by a   
cross gird] & ?is  op5+1 :i* c be       
revolv$ to any azimu? & c be clos$ by   
d\ble motor op]at$ %utt]s1 enables !    
telescope to obs]ve at any  "p ( ! sky4 

,auxili>y circul> ribs rea*+ f ! base r+
  up to ! ma9 ribs all ar\nd ! dome     
except at ! %utt] op5+1  =m ! support = 
! d\ble /eel cov]+ ( #ab in*es          
sep>ation4  ,?is v5tilat+ space is unit$
 ?r\gh suitable wea!r gu>ds )  ! space  
betwe5 ! build+ walls & =ms ! protection
 aga9/  ov]heat+ by ! sun 9 ! day "t4   
,dome ,accessories    ,! %utt] op5+ #af 
feet wide & ext5d+ f ! base ( !  dome to
 #f feet beyond ! z5i? is clos$ by a    
d\ble %utt] also  d\ble wall$ &         
v5tilat$4 ,canvas scre5s m\nt$ on tubes 
&  op]at$ by motor c be run up f ! base 
( ! %utt] op5+1  ?is "o be+ %[n 9 ,fig4 
#c1 & d[n f ! top s z to limit  ! op5+  
to ! wid? ( ! tube ( ! telescope4 ,^!   
scre5s  are necess>y :5 ! w9d is bl[+ to
 prev5t %ak+ ( ! tube  & consequ5t jump+
 ( ! /> image4 ,= enabl+ ! obs]v]  to   
rea* conv5i5tly ! upp] end ( ! telescope
 tube 9 any  position a c\nt]weight$    
elevat+ plat=m1 mov$ up & d[n !  %utt]  
op5+ by motor & drum ) lift+ cables is  
provid$4  ,?is plat=m is #bj feet long &

 #d feet wide ) a w+ at ea* end1  ext5d+
 inw>ds ab\t #f feet1 on :i* ! obs]v] c 
/& &  c move x & himself by a h& :eel up
 to & p>tly encircl+  ! telescope tube4 
,! plat=m & movable w+s1 :i* are well   
%[n 9 ,fig4 #c1 c be br\ght to any      
desir$ height by an op]at+  swit* at "o 
side & c be rea*$ by an auxili>y /airway
 f a  small /ation>y plat=m atta*$ to ! 
base r+ ( ! dome4 ,?is  /ation>y plat=m 
is rea*$ f ! obs]v+ floor by a p]man5t  
/airway mov+ ) ! dome & ext5d+ to a foot
 f ! floor4  ,plat=m w+s & /airways are 
made safe = obs]v]s by gu>d &  h& rails 
#cj in*es high4 ,?is mov+ plat=m1 an    
ess5tial accessory  = direct photography
 & o!r "w at ! pr9cipal focus ( !       
telescope1 meets1 9 a m conv5i5t &      
satisfactory mann] ?an any  o!r previ\s 
device = ! purpose1 all ! obs]v+        
requirem5ts  = "w at ! upp] end ( !     
tube4      ,me*anism = ,silv]+    ,9    
ord] to r5ew ! silv] coat+ on ! upp]    
surface ( !  mirror1 :i* is necess>y    
ab\t ?ree times a ye>1 me*anism has to  

be provid$ = h&l+ ! mirror & its cell1 !
 l[] section (  ! telescope tube1 ) ease
 & safety4 ,! mirror weighs ov] #b tons 
& ! cell #d tons1 s #f tons h to be     
remov$ f & replac$  on ! telescope tube4
 ,?is is effect$ by means ( ! silv]+    
c>1 :i* c be se5 at ! left ( ,fig4 #b1 a
 massive framework (  /ructural /eel    
roll+ on f\r flang$ :eels on flu% tracks
 9  ! obs]v+ floor4 ,) ! tube turn$ to a
 v]tical position1 !  c> is roll$ f its 
normal position at ! ea/ side ( ! dome  
directly "u ! tube & a motor-op]at$     
screw-jack surm\nt$ by  a triangul>     
rock+ arm c be br\ght up aga9/ ! bottom 
( !  cell4 ,on remov+ ! atta*+ bolts1   
cell & mirror c be l[]$  & roll$ on ! c>
 to ! ea/ out ( ! way4 ,! removal ( #f  
tons  f "o side ?r[s ! telescope out (  
balance & s ! outbo>d  end ( !          
decl9ation axis is support$ by a        
c\nt]weight$ /rut  run up ?r\gh ! floor 
& ! upp] end ( ! tube ti$ to r+s  at !  
top ( ! dome4 ,) a b& ( p>aff9$ pap] ti$
 ar\nd  ! edge ( ! mirror & a plug 9 !  

c5tral hole1 ! silv]+  solution c be    
p\r$ on & ev5ly fl[$ ov] ! surface by   
rock+  on a /eel ball at ! top ( !      
jack-screw4 ,:5 ! silv]+ is  complete1  
cell & mirror are replac$ 9 ! rev]se    
ord] & !  c> roll$ back out ( ! way4 ,! 
op]ation takes ab\t a day & is  p]=m$ ) 
p]fect safety & ease4    ,illu/ration3  
,fig4 #b4--,,telescope ,,9 ,,av]age     
,,obs]v+ ,,position          ,,section  
#c4--,,me*anical ,,p>ts ,,( ,,telescope 
,introduction    ,x is useful1 be=e     
describ+ ! me*anical p>ts or m\nt+ (  ! 
telescope1 to expla9 ! diff]5ce betwe5 !
 two k9ds (  telescope1 refract+ &      
reflect+1 employ$ 9 a/ronomical "w4  ,! 
refract+ telescope is ! mo/ famili> type
 z ! ord9>y  spyglass or draw-tube      
telescope & ! field or op]a glass are   
all  refract+ telescopes4 ,! refract+   
telescope is s call$ because  ! light f 
! di/ant object is refract$ ?r\gh a l5s 
at !  out] end ( ! tube & =ms an image (
 ! object at ! inn]  end1 j z a cam]a   
=ms an image on ! gr\nd glass or film1 &

  ?is image is view$ & magnifi$ by !    
eyepiece or ocul>4 ,!  reflect+         
telescope on ! o!r h& has ! upp] or out]
 end  ( ! tube op5 & ! light f ! di/ant 
object is reflect$  7h5ce ! "n7 f a     
concave mirror at ! l[] end ( ! tube1   
=m+ ! image ( ! object at ! top1 :]e x c
 be view$ &  magnifi$ by ! ocul> z 9 !  
refractor4    ,ea* type ( telescope has 
its a/ronomical advantages &            
disadvantages4 ,! refractor is bett]    
suit$ = visual obs]vations  su* z !     
measurem5t ( d\ble />s & ! /udy (       
planet>y  detail & is less affect$ by   
temp]ature *anges ?an ! reflector4  ,on 
! o!r h& ! reflector1 on acc\nt ( its   
p]fect a*romatism1  is ! in/rum5t p>    
excell5ce = photographic obs]vations1 &1
 z  m ?an ?ree-f\r?s ( mod]n a/ronomical
 "w is photographic1 x  appe>s to be    
sup]s$+ ! refractor4 ,?is advantage is  
increas$  by ! fact t ! refractor has   
app>5tly rea*$ ! useful  limit 9 size & 
t x co/s at lea/ ?ree times z mu* z a   
reflector ( ! same ap]ture4 ,al?\gh ea* 

type ( telescope has  its *>act]i/ic    
type ( m\nt+ = a/ronomical purposes1 !  
pr9ciples are ! same = ea* & c probably 
be mo/ easily  foll[$ by describ+ !     
ess5tial p>ts ( ! m\nt+ ( !  #gb-;in*   
telescope4      ,! ,telescope ,tube     
,! tube p]=ms ! important function (    
c>ry+ 9 relatively  inv>iable position &
 adju/m5t ! optical p>ts ( ! telescope4 
,! tube ( ! #gb-;in* telescope is #ca   
feet long1 #g feet #d in*es  out]       
diamet] & weighs #ae tons4 ,its =m &    
con/ruction are well  %[n 9 ,figs4 #b & 
#c4 ,x consi/s ( ! ma9 or c5tral section
  ,a1 ,fig4 #b ! l[] section ,b :i*     
c>ries ! ma9 mirror & !  skeleton       
section ,c :i* c>ries ! second>y        
mirrors4 ,! c5tral  section is a        
cyl9drical /eel ca/+ heavily ribb$ on ! 
inside  ab\t #f feet high & weighs #g   
tons4 ,! l[] section is securely  bolt$ 
to x ?r\gh ! flanges %[n & ) ! mirror & 
its  support+ me*anism weighs ab\t #f   
tons4 ,! upp] skeleton section  is built
 up ( /ructural /eel1 #c in* ,i beams1  

firmly brac$ &  rivett$ toge!r 9 ! mann]
 %[n 9 ! figures4 ,a special  feature ( 
?is skeleton tube1 mak+ x m rigid ?an   
any previ\s  design1 consi/s ( !        
diagonal t5sion rods 9 ea* rectangul>   
comp>tm5t screw$ up ea* to a t5sion (   
ab\t #b1jjj p\nds1 s  t ! :ole tube is  
"u t5sion 9 e position4 ,?is /iffness   
is ess5tial = ! prop] p]=mance ( !      
optical p>ts1 z !  pr9cipal & second>y  
mirrors at bottom & top ( tube          
respectively  %\ld occupy ! same        
relative positions 9 :atev] direction ! 
tube is po9t$4      ,! ,decl9ation ,axis
    ,! telescope tube is firmly screw$  
at "r angles to ! flang$ end  ( a       
massive %aft #af in*es 9 diamet]1 call$ 
! decl9ation axis1  ext5d+ ?r\gh !      
cubical section ,d ( ! pol> axis ,,nds1 
,fig4 #b1  ?r\gh ! decl9ation sleeve ,e 
into ! h\s+ ,f4 ,?is decl9ation  axis is
 rotat$1 c>ry+ ! tube ) x1 on ball be>+s
 9 ,d &  ,f1 ?is rotation be+ effect$ by
 an electric motor ) r$uction  me*anism1
 ge>+ into a l>ge spur ge> atta*$ to !  

end ( !  decl9ation axis1 ! :ole be+    
conceal$ )9 ! decl9ation  h\s+ ,f4 ,h5ce
 ! tube c be turn$ at ! rate ( #de      
degrees to  ! m9ute to any requir$      
position up or d[n1 nor? or s\?4 ,!     
position 9 ! sky1 ! decl9ation1         
correspond+ to latitude on !  e>?1 is   
read on a l>ge circle graduat$ into     
degrees )9 ,f &  subdivid$ into #e m9ute
 int]vals on ! small auxili>y circle ,h4
      ,! ,pol> ,axis    ,z positions    
nor? or s\? are giv5 by turn+ ! tube on 
!  decl9ation axis1 s positions ea/ or  
we/ are giv5 by rotation on  ! pol>     
axis1 s call$ because x po9ts to ! pole 
( ! heav5s  & is exactly p>allel to !   
axis ( ! e>?4 ,! ,pol> axis ,,nds  ,fig4
 #b1 :i* is #ba feet long & weighs #ie  
tons1 is built up (  ?ree /eel ca/+s1 a 
c5tral cubical section ,d & two conical 
end  sections1 all securely bolt$ toge!r
 & turn+ 9 ball be>+s  on its ends4 ,!  
upp]1 nor?1 be>+ is c>ri$ 9 an adju/able
  pill[ block1 by :i* ! f9al p>allelism 
) ! e>?'s axis is  obta9$1 bolt$ on !   

curv$ cem5t pi] %[n at ! left or nor?  9
 ,figs4 #b & #c4 ,! l[]1 s\?1 be>+ is   
c>ri$ 9 a massive  ca/ iron p$e/al bolt$
 to ! s\? cem5t pi]4 ,! pol> axis is    
rotat$ on ^! be>+s1 also at ! rate ( #de
 degrees p] m9ute1  c>ry+ ! decl9ation  
axis & tube ) x to any position ea/ or  
we/ 9 ! sky by an electric motor &      
r$uction ge>+ conceal$  )9 ! s\? p$e/al4
 ,! position ea/ or we/ 9 ! sky1 !  "r  
asc5sion z x is call$ correspond+ to    
longitude on !  e>?1 is read by means ( 
a graduat$ circle %[n above ,g1 ,fig4   
#b1  :i* is divid$ into #bd h\rs & ea*  
h\r into s+le m9utes4 ,:ile  longitudes 
on ! e>? are occasionally express$ z s  
_m h\rs  & m9utes ea/ or we/ ( ,gre5wi*1
 "r asc5sions 9 ! sky are  almo/        
inv>iably giv5 9 h\rs & m9utes r ?an    
degrees4    ,illu/ration3 ,fig4         
#c4--,,telescope ,,f ,,! ,,we/      ,!  
,driv+ ,clock    ,x is evid5t1 by       
rotation ( ! telescope on ! decl9ation &
  pol> axes by means ( ! quick-motion   
motors1 t ! tube c be  po9t$ 9 any      

direction 9 ! sky1 t[>ds any />4 ,b ow+ 
to !  rotation ( ! e>? on its axis f we/
 to ea/1 :i* is ! cause  ( ! app>5t     
motion ( sun1 moon & />s f ea/ to we/1 !
  telescope w be quickly c>ri$ ea/w>d ( 
! /> :i* w only  rema9 = an in/ant 9 !  
field4    ,! me*anism by :i* ! rotation 
( ! e>? is comp5sat$ =  is call$ ! driv+
 clock & is conta9$ 9 ! case ,l1 ,fig4  
#b1  at ! nor? side ( ! s\? pi]4 ,9 !   
l[] half ( ! case a  gov]nor simil> to !
 gov]nor ( a /eam eng9e is driv5 once p]
  second by a tra9 ( ge>s 9 ! upp]      
section actuat$ by a weight  ( #cjj     
p\nds bel[ ! floor4 ,if ! spe$ ( !      
gov]nor t5ds to  increase ! balls raise 
by c5trifugal =ce & br+ increas$        
friction to be> ?us r$uc+ ! spe$ to     
normal :ile if ! spe$  t5ds to decrease1
 ! balls drop & r$uc$ friction quickly  
all[s  x to accel]ate to normal spe$4 ,a
 %aft ) a co>se screw ?read  on x1 call$
 te*nically a 8worm0 & situat$ at ! top 
( !  case1 is driv5 by int]m$iate ge>+ f
 ! gov]nor at !  rate ( "o revolution e 

two m9utes4 ,! ?read on ?is %aft        
engages into tee? cut 9 ! worm :eel ,g1 
,fig4 #b1 :i* is #i feet 9  diamet]4 ,z 
!re are #gbj tee? v accurately spac$ 9  
?is worm  :eel1 x is driv5 ar\nd by !   
worm 9 #b  #gbj  #a1ddj m9utes1 #bd     
h\rs1 ! same rate z ! e>?4 ,?is worm    
:eel1 normally loose  on ! pol> axis on 
:i* x turns on ball be>+s1 all[+ !  axis
 to be mov$ freely to any position1 c be
 rigidly clamp$ to x  by press+ a       
button4 ,:5 ?is is done1 x w evid5tly   
turn !  pol> axis & h5ce ! tube at !    
same rate z ! e>? b 9 !  opposite       
direction1 on an axis p>allel to ! axis 
( ! e>?1 ?us  exactly comp5sat+ = !     
rotation ( ! e>?4 ,h5ce any />  at :i* !
 telescope is po9t$ w automatically     
rema9 c5tral  9 ! field4 ,ow+ to ! great
 magnification all ?is me*anism         
requires ! highe/ grade ( workman%ip1   
else !re w be w&]+  ( ! image1 a mo/    
annoy+ & tr\blesome defect4 ,few        
telescopes  are entirely free f p]iodic 
error & t ! #gb-;in* drives  s regul>ly 

& smoo?ly is a great advantage & evid5ce
 ( !  p]fection ( workman%ip ?r\gh\t4   
,electric ,motions    ,x has already be5
 describ$ h[ ! telescope c be mov$ by   
motors  nor? or s\? & ea/ or we/ at !   
rate ( #de degrees p] m9ute4  ,^! motors
 are op]at$ f small swit*bo>ds on ea*   
side (  ! s\? pi]1 ! "o at ! we/ be+ se5
 9 ,figs4 #b & #c4 ,!  left-h& rev]s+   
swit* moves ! telescope ea/ or we/1 !   
c5tre swit* nor? or s\? & ! "r-h& swit* 
revolves !  dome ea/ or we/4 ,9 addition
 to ^! quick motions ( ! telescope  =   
rapidly br++ x to ! approximate         
position1 mu* f9] &  sl[] motions are   
requir$ = br++ ! image exactly c5tral & 
= guid+4 ,^! sl[ motions are also op]at$
 by electric motors  actuat$ by two     
small alum9ium swit*bo>ds atta*$ by     
flexible  cables to ! top & bottom ( !  
tube4 ,^! swit*bo>ds c be  c>ri$ 9 ! h&s
 ( ! obs]v] or re/$ on ! obs]v+  ladd]4 
,pressure on suitable buttons moves !   
telescope nor? or  s\?1 ea/ or we/ at   
ei!r "o ( two diff]5t spe$s1 a spe$ (   

"o revolution 9 #cf h\rs = c5t]+ ! image
 & a spe$ ( "o  revolution 9 #cj days = 
guid+1 correct+ = slight irregul>ities  
due to air di/urbance or o!r causes4    
,al?\gh ^! spe$s may seem  excessively  
sl[1 ! motion ( ! image ev5 ) ! mon?ly  
rate  is at once evid5t on press+ !     
button & fa/] spe$s w\ld make  accurate 
guid+ difficult4 ,9 addition to ! two   
quick & two sl[  motion motors !re are  
two clamp+ motors & "o = automatically  
rew9d+ ! clock weight1 sev5 9 all4 ,^! )
 ! ?ree motors  op]at+ ! dome are all   
cont9u\s curr5t motors :i* c be  />t$ & 
rev]s$ m readily & h great] initial     
torque ?an  alt]nat+ motors4 ,ea* motor 
is suppli$ ) an automatic control1  s t 
all t is necess>y is to ?r[ ! swit* or  
press !  button to />t or rev]se4       
,curr5t is suppli$ by a motor g5]ator   
set on ! gr\nd floor4      ,me?od (     
,op]ation    ,a description ( ! me?od ( 
sett+ ^u ! requir$ />1 :51  = example1  
photograph+ ! spectra ( ! />s1 w help to
 make  ! op]ation ( ! telescope m cle>ly

 und]/ood4 ,x is easily  possible to    
pull ! telescope ar\nd by h& to !       
requir$ />  id5tifi$ by eye among !     
con/ellations4 ,al?\gh ! mov+ p>ts  ( ! 
telescope weigh ne>ly #de tons1 s p]fect
 are ! ball be>+s  9 :i* x turns t a    
weight ( #c p\nds at ! upp] end ( !     
tube is suffici5t to set x 9 motion4    
,h[ev] ! sett+s c be  mu* m quickly &   
c]ta9ly made by turn+ ! telescope to !  
"r asc5sion & decl9ation ( ! /> by !    
electrical motions4  ,a programme ( !   
/>s to be obs]v$ ) _! "r asc5sions &    
decl9ations is prep>$ be=eh&4 ,! obs]v+ 
assi/ant /&s  beside ! small swit*bo>d  
on ! s\? pi] & rapidly moves !          
telescope ea/ or we/ & nor? or s\? until
 ! indexes on !  graduat$ circles po9t  
to ! tabulat$ positions1 :ile ! dome c  
be turn$ to ! requir$ position at ! same
 "t by means ( !  ?ird op]at+ swit*4 ,by
 press+ two buttons ! telescope is !n   
firmly clamp$ & ! driv+ clock />ts !    
telescope automatically  foll[+ ! />4 ,9
 ! meantime ! obs]v] has ins]t$ !  plate

 hold] 9 ! spectrograph & drawn ! slide 
& by means (  ! alum9ium swit*bo>d br+s 
! />1 :i* is g5]ally ne> !  c5tre1      
exactly to ! c5tre ( ! f9d]1 :5 x w be  
visible on  ! slit ( ! spectrograph     
?r\gh a guid+ eyepiece & c quickly  be  
br\ght c5tral & ! exposure comm5c$4 ,!  
"t requir$ f  ! end ( "o exposure to !  
beg9n+ ( ! next1 unless ! />s  are f>   
ap>t 9 ! sky1 does n g5]ally exce$ two  
m9utes1 a  %ort] "t ?an usually requir$ 
= ev5 q small telescopes4  ,?is rapid   
op]ation is due to special c>e 9 design 
& con/ruction  & m>k$ly increases !     
effici5cy & capacity ( ! in/rum5t4      
,special ,features ( ! ,m\nt+    ,!     
m\nt+ ( ! #gb-;in* telescope has sev]al 
new features n  hi!rto us$ & sets a new 
/&>d = conv5i5ce & accuracy (  op]ation4
 ,! obs]vatory is mu* indebt$ to ! ,w>n]
  ,swasey ,co41  :o h made mo/ ( ! l>ge 
m\nt+s 9 ,am]ica1 = ! _s 9  :i* !y      
und]took & c>ri$ ?r\gh ?is "w4 ,_! sole 
object  0 to produce ! be/ possible     
m\nt+ reg>dless ( co/ & no  sugge/ion ( 

! writ] look+ to improvem5t 0 refus$4   
,to ,mr4  ,swasey1 ! presid5t1 are due  
_m ( ! orig9al features ( !  m\nt+ & !  
beauty & h>mony ( ! design1 :ile ,mr4   
,burrell1  ! works manag]1 is           
responsible = ! simplification ( !      
me*anism & ! beautiful co-ord9ation ( ! 
details4 ,no great]  te/imony to !      
p]fection ( design & con/ruction c be   
giv5  ?an to say t aft] five ye>s use   
!re is no feature ! director  w\ld wi%  
*ang$1 & no s+le defect ( con/ruction   
has be5  reveal$4    ,x may be ( int]e/ 
to note ! pr9cipal improvem5ts 9 ?is    
m\nt+4    #a4 ,all p>ts ( ! sky c be    
readily rea*$4 ,?is is n possible  ) all
 types ( reflect+ telescopes4    #b4 ,! 
elim9ation ( cyl9drical be>+s ) cumbr\s 
friction-reliev+ devices1 =m]ly consid]$
 necess>y =  ma9ta9+ collimation &      
adju/m5t on decl9ation & pol>  axes1 & !
 use ( ball be>+s = bo? friction-reliev+
 &  collimat+ purposes has result$ 9    
rem>kable ease ( movem5t ( !  telescope4
    #c4 ,fre$om f p]iodic or o!r errors 

9 driv+ & smoo?ness &  fre$om f         
8backla%0 9 sl[ motions4    #d4 ,ease1  
spe$ & accuracy ) :i* sett+s c be made  
due to  c>eful design & orig9al features
 9 sett+ motors & sett+  circles4    #e4
 ,great /iffness ( tube & improvem5ts 9 
me?od ( atta*+ &  *ang+ second>y        
mirrors4    #f4 ,beauty & h>mony (      
design & appe>ance4          ,,section  
#d4--,,optical ,,p>ts ,,&               
,,spectrographs      ,! ,pr9cipal       
,mirror    ,! great mirror is compos$ ( 
h>d plate glass ca/ 9 "o piece &  aft]  
anneal+1 gr\nd & poli%$ to ! correct    
%ape4 ,z receiv$  f ! ,/4 ,goba9 ,co41 !
 disc 0 #gce in*es diamet]1 ov] #ac     
in*es ?ick ) a c5tral hole ab\t #f in*es
 diamet] & weigh$  ne>ly #e1jjj p\nds4  
,x 0 fir/ ( all gr\nd truly circul> to a
  diamet] ( #gc in*es & flat on bo?     
sides to a ?ickness ( slightly  ov] #ab 
in*es1 :ile ! c5tral hole 0 enl>g$ to   
#aj in*es4 ,:5  ! back 0 poli%$         
approximately flat1 ! disc 0 se5 to be a
  beautiful specim5 ( ! glass mak]s art1

 homog5e\s & almo/  entirely free f     
bubbles or o!r defects4    ,illu/ration3
 ,fig4 #d4--,,photograph ,,( ,,r+       
,,nebula ,,9 ,,lyra    7,enl>g$ #h      
diamet]s7    ,x 0 n[ ready = ! second   
/age ( ! op]ation ! gr9d+  ( ! correct  
%ape = ! upp] reflect+ surface4 ,9 ord] 
to  br+ ! light ( a /> to an accurate   
focus ?is surface mu/  be a p>aboloid ( 
revolution1 ! same k9d ( curve giv5 to !
  reflectors ( se>* lights or automobile
 headlights4 ,! curve =  ?is reflector (
 #cj feet focus is v ne>ly a section ( a
 sph]e (  #fj feet radius1 )9 "o-?\s&? (
 an in*1 & consequ5tly  w\ld ne>ly fit a
 huge globe #abj feet 9 diamet]4 ,! upp]
 surface  ( ! disc 0 f9e gr\nd & poli%$ 
to ?is sph]ical surface &  0 !n ready = 
! f9al /age1 ! 8figur+0 a cont9uation ( 
! poli%+ process until ! c5tre is deep5$
 ab\t a ?\s&?  ( an in* & ! surface     
becomes accurately p>aboloidal4 ,?is    
8figur+10 an exce$+ly delicate &        
difficult process especially  ov] su* a 
l>ge surface z ! #gb-;in*1 ) ! add$     

difficulty (  a c5tral hole1 occupi$    
ab\t two ye>s & 0 n complet$ until      
ne>ly a ye> & a half aft] ! m\nt+ 0     
ready4 ,:5 x is  rememb]$1 h[ev]1 t !   
surface n[h]e deviates f ! true         
!oretical =m m ?an "o f\r-hundr$-?\s&? (
 an in* &  t if "o "p is accid5tally    
poli%$ too deep1 ! :ole surface  has    
aga9 to be br\ght d[n to ?is level1 !   
exce$+ delicacy (  ! op]ation is evid5t 
& ! "t tak5 n excessive4    ,accurate   
quantitative te/s %[$ t ! f9al figure is
 ( !  highe/ ord] ( accuracy & ?is is   
fur!r cle>ly %[n by !  practical te/ (  
direct photographs at ! pr9cipal focus4 
,figure  #d1 a six fold enl>gem5t ( a   
photograph at ! pr9cipal focus1 (  ! ,r+
 ,nebula 9 ,lyra %[s h[ %>p & small are 
! /> images4  ,actual measurem5t on !   
orig9al negative gives a m9imum diamet] 
( two "o-?\s&?s ( an in* equival5t to   
only a second ( arc  at ! focus4 ,z !   
images are enl>g$ consid]ably by        
un/ead9ess  ( ! air & errors 9 guid+ !  
/> light reflect$ f !  :ole surface ( ! 

mirror is collect$ into a little disc   
less ?an a  ?\s&? ( an in* 9 diamet]    
indicat+ ! extraord9>y accuracy  ( !    
reflect+ surface4 ,mr4 ,j4 ,b4          
,mc,dowell1 head ( ! firm s9ce  ,dr4    
,bra%e>'s dea?1 & ,mr4 ,fr$ ,hegemann1 8
 *ief optician1 are  to be highly       
congratulat$ on ! p]fection ( figure    
obta9$ "u  specially difficult          
circum/ances4 ,fur!r ! f9e r5d]+ ( !    
detail 9 ! r+ & ! /r5g? ( ! two b&s 9 ! 
int]ior  indicate n only p]fect figure b
 exceptionally high poli%4      ,m\nt+ (
 ,mirror    ,?is mirror1 to ma9ta9 its  
accuracy1 n only requires c>eful  m\nt+ 
9 its cell b also protection aga9/      
temp]ature *anges4  ,ev5 ?\gh #ab in*es 
?ick x w\ld b5d "u its own weight (     
#d1cjj  lbs4 suffici5tly to affect !    
figure & consequ5tly x is support$  9 ! 
cell by a specially c\nt]weight$ lev]   
sy/em s t x is  equably support$ at     
twelve po9ts & !re is no t5d5cy to b5d4 
,a simil> lev] support sy/em ar\nd !    
edge prev5ts di/ortion  due to con/ra9t 

:5 x is tipp$ f ! horizontal position at
  diff]5t positions ( ! tube4           
,temp]ature *anges c produce mu*  great]
 di/ortion ?an flexure b ,victoria has !
 advantage ( v  l[ diurnal range & !    
temp]ature *ange ar\nd ! mirror is made 
v small by a lagg+ ( cotton felt ab\t #b
 in*es ?ick all r\nd  ! sides ( ! clos$ 
section ( ! tube1 lac$ on ) a duck  cov]
 7comp>e ,fig4 #c ) ,fig4 #b7 & an equal
 ?ickness bel[ &  ar\nd ! edge ( !      
mirror4 ,by ?is lagg+ ! temp]ature rise 
9  ! day-"t is only ab\t half a degree  
:ile ! dome temp]ature  increases five  
degrees1 h5ce ! figure ( ! mirror rema9s
 good  :atev] ! temp]ature *anges       
outside4      ,! ,pr9cipal ,focus    ,z 
already indicat$1 ! pr9cipal mirror :5  
us$ alone =ms an  image ( ! /> #cj feet 
above1 at ! c5tre ( ! upp] end (  !     
tube1 & an eyepiece c\ld be plac$ !re = 
visual "w or a  photographic plate =    
direct photographs ( nebulae1 etc4      
,h[ev]1 x  is g5]ally m conv5i5t to use 
a flat mirror at #de =m+ !  image at !  

side ( ! tube = photographs & s !       
telescope is  only us$ 9 ?is =m ) a     
small spectrograph = ! ultra-violet     
region ( /> spectra4 ,! c\rse ( !       
p>allel beam ( light f  ! /> to its     
image on ! slit ( ! spectrograph is     
graphically  %[n 9 ,fig4 #e ,a & also   
its passage ?r\gh ! slit prisms &  l5ses
 ( ! spectrograph4 ,! position ( ! />   
image on ! slit  ( ! spectrograph c be  
obs]v$ by a guid+ telescope ext5d+  to !
 edge ( ! tube & c be kept c5tral by !  
portable  alum9ium swit*bo>d already    
describ$4 ,! elevat+ plat=m is (  c\rse 
us$ 9 "w 9 ?is position4      ,!        
,newtonian ,arrangem5t    ,= direct     
photography or visual obs]vations at !  
focus ( !  #gb-;in* mirror1 ! reflect$  
cone ( /> light f ! mirror ,b1  ,fig4   
#e1 is int]cept$ by a plane mirror also 
silv]$ on ! front  surface1 #aie in*es  
diamet] & #cbe in*es ?ick plac$ at #de4 
,?is  =m ( reflect+ telescope 0 fir/ us$
 by ,newton1 h5ce ! "n4  ,! focus is !n 
=m$1 z %[n1 at ! side ( ! tube1 & if a  

plate is plac$ !re & accurately guid$ by
 small eyepieces )  cross wires1        
photographs ( any desir$ small region 9 
! sky c be  obta9$1 ,fig4 #d be+ made 9 
?is position1 or visual obs]vations  may
 be made4 ,! ocul>s c easily be rea*$ f 
! obs]v+  plat=m = any position ( !     
telescope4      ,! ,cassegra9           
,arrangem5t    ,! mo/ g5]ally useful    
arrangem5t ( ! #gb-;in* telescope is1   
h[ev]1 ! ,cassegra9 =m1 s call$ f !     
,fr5* a/ronom] :o  fir/ us$ x4 ,ab\t #g 
feet bel[ ! focus1 ! conical reflect$   
p5cil f ! #gb-;in* mirror is int]cept$  
by a convex mirror (  ! same size z !   
,newtonian & ( ab\t #aj feet focal l5g? 
z  se5 9 ,c1 ,fig4 #e1 & also %[n 9     
,fig4 #b & #c4 ,?is mirror turns  !     
light d[nw>d &1 aft] pass+ ?r\gh !      
c5tral hole1 =ms  ! image ( ! /> ab\t   
two feet bel[ ! mirror surface on !     
slit ( ! spectrograph or on a visual    
atta*m5t z %[n4 ,!  significant prop]ty 
( ?is comb9ation is t ! focal l5g? is   
increas$ f #cj to #ajh feet )\t *ang+ ! 

tube l5g? 9 a  some:at simil> mann] to !
 action ( a telephoto l5s4 ,x has !     
same size ( image & magnify+ p[] z a    
refractor ) a tube #ajh  feet long & has
 ! decid$ advantage ( a mu* %ort] tube &
  small] dome4 ,obs]vations ) ?is       
arrangem5t are made at ! l[]  end ( !   
tube f ! obs]v+ floor & ) mu* great]    
ease  & conv5i5ce ?an at ! upp] end4    
,*anges f ! ,cassegra9 to  ! ,newtonian 
or ,pr9cipal ,focus arrangem5ts are     
readily effect$ by  a device due to !   
g5ius ( ,mr4 ,swasey :]eby only !       
mirrors &  atta*+ tubes require to be   
h&l$1 in/ead ( ! :ole upp] end  ( ! tube
 z 9 previ\s reflectors4                
,illu/ration3 ,fig4 #e4--;,,c\rse ,,(   
,,light ,,9 ,,telescope ,,f ,,/> ,,to   
,,focus      ,accessory ,optical ,p>ts  
,a full set ( eyepieces giv+ magnify+   
p[]s f #abj to #e1jjj  diamet]s & a     
complete d\ble-slide plate hold] ) guid+
  eyepieces = direct photography at !   
,newtonian focus are provid$4  ,9       
addition !re is a visual atta*m5t %[n 9 

diagram ,c1 ,fig4 #e1  :i* enables !    
telescope to be us$ visually at !       
,cassegra9 focus  )\t remov+ !          
spectrograph4 ,!re are ?ree f9d]s atta*$
  to ! telescope tube = pick+ up & c5t]+
 ! />s4 ,two (  #d in* ap]ture & #e feet
 focus1 ( p[] ab\t #ej1 "o nor?1 "o  s\?
 on ! tube1 & a long focus tubeless f9d]
 ) a l5s ( #g  in* ap]ture & #cj feet   
focus at ! top ( ! telescope tube & an  
ocul> ( p[] #bjj at ! bottom4      ,!   
,spectrographs    ,mo/ ( ! a/ronomical  
"w ) ! #gb-;in* telescope is            
spectroscopic1 photograph+ ! spectra ( !
 />s1 & s a  description ( ! pr9ciples &
 op]ation ( spectrographs is  desirable4
 ,/ell> spectrographs h evolv$ into     
c]ta9 def9ite  =ms & ! two spectrographs
 = ! #gb-;in* telescope are examples  ( 
! mo/ rec5t types4 ,9 ess5ce a          
spectrograph consi/s ( a  n>r[ slit1 "o 
or two-?\s&?s ( an in* wide1 on :i* !   
/> light is focuss$4 ,t pass+ ?r\gh !   
slit falls on !  collimator l5s :i*     
makes x p>allel & !n on a prism or      

prisms1  triangul> %ap$ pieces ( glass  
:i* *ange ! direction ( !  light &      
decompose x1 break+ x up into its       
con/itu5t ra9b[  col\rs4 ,! spectrum1 z 
x is call$1 is focuss$ by a cam]a l5s on
  a photographic plate or c be view$ by 
a small telescope if desir$4  ,! c\rse (
 ! /> light f ! slit ?r\gh collimator1  
prism  & cam]a l5s to ! plate is %[n 9  
,c1 ,fig4 #e1 :ile a view ( !           
,cassegra9 spectrograph %[+ ! int]ior   
me*anism & accessories  is giv5 9 ,fig4 
#f4 ,! "p ( ! spectrum photograph$ is   
usually  only ! blue & violet region to 
:i* ! ord9>y plate is mo/  s5sitive1 &  
obvi\sly no col\rs appe> on ! negative b
 only a  n>r[ d>k /rip :i* is cross$ by 
light or d>k l9es4 ,x is f  ! numb] &   
position ( ^! l9es t we obta9 su* a     
rem>kable  am\nt ( in=mation ab\t !     
physical & *emical con/itution1 !       
temp]ature1 motion & di/ance ( ! />s4 ,!
 l5g? ( ! />  spectrum photograph$ ) "o 
prism is ab\t "o & a ?ird in*es1  twice 
& ?ree times t ) two & ?ree prisms4 ,its

 wid? is  ab\t "o-hundr$? ( an in* & 9  
ord] to make x ?is wide !  /> image has 
to be mov$ back & =w>d along ! slit4 ,! 
l5g?  ( spectrum ) ! ultra-violet       
spectrograph1 :i* only diff]s f  ! o!r 9
 ! prisms & l5ses all[+ ! spectrum bel[ 
!  violet to pass1 is ab\t "o in*4 ,a   
photograph ( ! spectrum ( iron  or brass
 is made beside ! /> spectrum to s]ve z 
a /&>d to  det]m9e ! positions ( ! />   
l9es4    ,illu/ration3 ,fig4            
#f4--,,/ell> ,,spectrograph ,,arrang$   
,,= ,,use ,,) ,,"o  ,,prism             
7,,temp]ature ,,case ,,remov$7          
,me?od ( ,use    ,e t]re/rial elem5t    
gives gr\ps ( l9es 9 c]ta9 positions  9 
! spectrum & if we f9d simil> gr\ps 9 ! 
/> spectrum  we are sure ?is elem5t is  
pres5t 9 ! />4 ,fur!r if we f9d  ^! l9es
 are displac$ to r$ or violet ( _!      
normal position  we "k t ! /> is rec$+ f
 or approa*+ to u4 ,)  ! "o-prism       
spectrograph a spe$ ( "o mile p] second 
means a  displacem5t ( ! l9es ( "o      
?irty-?\s&? ( an in*4 ,?us  if ! l9es   

are %ift$ to ! violet by a ?\s&? ( an   
in*1  ! /> is approa*+ ! e>? ) a spe$ ( 
#cj miles a second4  ,^! displacem5ts   
are accurately measur$ by a microscope &
 !  measurem5t ( ! radial velocities ( !
 />s is "o ( ! ma9  rese>*es ( ?is      
obs]vatory4 ,obvi\sly ) su* small       
displacem5ts  to be measur$ ! greate/   
c>e mu/ be tak5 to avoid all s\rces  (  
error4 ,! spectrograph mu/ be           
exceptionally rigid to avoid  diff]5tial
 b5d+ z x moves ) ! telescope4 ,z *ange 
(  temp]ature c produce spuri\s %ifts ( 
! l9es1 ! temp]ature  mu/ be kept z     
con/ant z possible1 ?is be+ effect$ "h  
by  a v accurate electrical !rmo/atic   
device call$ ! ,cal5d>  ,record] :i*    
ma9ta9s ! temp]ature con/ant to         
"o-hundr$? (  a degree4 ,! optical p>ts 
mu/ be ( ! highe/ quality to give       
p]fect def9ition to ! spectrum l9es & _m
 o!r precautions  mu/ be tak5 if        
accurate "w is desir$4 ,! spectrographs 
( !  #gb-;in* telescope h unequall$     
def9+ p[] & are ! la/ ^w  9 conv5i5ce ( 

manipulation & accuracy ( "w4    ,ow+ to
 ! fa9tness ( ! /> light & to its be+   
spread out  into a spectrum a           
consid]able "t is requir$ to photograph 
!  spectrum ( a />1 ab\t #bj m9utes = ! 
six? magnitude1 ! limit  ( visibility to
 ! unaid$ eye1 :5 photograph$ ) "o      
prism1  :ile ?ree prisms w take ne>ly   
five times z long4 ,h5ce !  necessity & 
use ( l>ge telescopes is n to get high  
magnify+  p[] b to collect suffici5t    
light f ! fa9t] />s to enable  _!       
spectra to be photograph$ or o!r        
obs]vations made4          ,,section    
#e4--,,! ,,"w ,,( ,,! ,,telescope       
,preval5t ,misconceptions    ,! g5]al   
idea ( an a/ronom]'s "w1 z ga!r$ f !    
que/ions & rem>ks ( visitors1 is t he   
sits at ! eyepiece (  ! telescope sweep+
 ! heav5s 9 a se>* = new planets1 comets
  or />s4 ,! absolute futility ( su* a  
use ( ! telescope is  evid5t :5 x is    
realiz$ t ! ma9 field ( ! #gb-;in* cov]s
  only ab\t "o hundr$-million? ( ! sky &
 if only five seconds  0 requir$ to     

exam9e ea* field x w\ld take m ?an a    
lifetime  to g ov] ! :ole sky once4 ,a  
second misconception is ! idea t  l>ge  
telescopes are us$ = visual obs]vations 
( ! planets )  special ref]5ce to _!    
habitability4 ,no "w is be+ attempt$  at
 ?is or o!r l>ge obs]vatories on        
planet>y detail = :i*  ab\t an #ah-;in* 
refractor gives ! be/ results & su* a   
l>ge  telescope z ! #gb-;in* is q       
unsuit$4 ,all sci5tific obs]vations  ) !
 #gb-;in* are made photographically & x 
is only arrang$ =  visual use on        
,saturday ev5+s :5 = two h\rs visitors  
are all[$  to obs]ve ! heav5ly bodies4  
,a ?ird misconception is t !  a/ronom]  
only works at night4 ,h[ev] true ?is    
idea may h be5  9 ! days ( visual       
obs]vations :5 ! measurem5ts 7 made at  
! eyepiece1 !re is c]ta9ly n[1 :5       
photography is s g5]ally  appli$1 m day 
?an night "w 9 a/ronomy4 ,besides !     
advantages  ( p]man5cy1 accuracy (      
measurem5t & p[] ( record+ objects      
beyond ! range ( ! ke5e/ eyesight1 !    

photographic me?od has  ! fur!r great   
advantage t an h\r's exposure may give  
suffici5t  mat]ial = sev]al days'       
measurem5t & discussion4                
,spectroscopic ,"w    ,z already        
indicat$ mo/ ( ! "w ) ! #gb-;in*        
telescope  is spectroscopic1 b z also   
indicat$ mod]n spectroscopic            
inve/igations cov] s wide a range (     
rese>* t ! actual "w  ( ! obs]vatory is 
v v>i$4 ,by aid ( suitable spectrographs
  atta*$ to a l>ge telescope we c       
measure ! spe$ ( ! />s  t[>ds or f u1 _!
 radial velocity z x is t]m$4 ,we c     
discov] d\ble />s too close ev] to be   
se5 d\ble 9 any telescope  & we c       
det]m9e ! mann] 9 :i* !y revolve ar\nd  
"o  ano!r & _! di/ance ap>t & mass4 ,f !
 spectra ( !  />s we c det]m9e _!       
absolute brightness z comp>$ ) !  sun & 
_! p>allax or di/ance4 ,! *emical       
elem5ts pres5t 9  ! out] atmosph]es ( ! 
/>s c be det]m9$ & ! pressure  9 ^!     
atmosph]es4 ,! measurem5t ( temp]atures 
& o!r  physical conditions 9 ! />s by   

means ( ! spectroscope is n[  an        
accompli%$ fact & "o ( ! mo/ rec5t      
developm5ts ( !  spectroscopic "w "h has
 be5 to provide evid5ce ( ! tru? (  a   
!ory ( atomic /ructure & to %[ t !      
atomic con/ants 9  ! enorm\s furnaces ( 
! />s are ! same z on ! e>?4 ,su*  a    
catalogue ( in=mation1 obta9$ f an      
inve/igation ( ! m]e  quality ( ! light 
f />s s fa9t z to be q invisible to  !  
unaid$ eye & s di/ant t x may take ?\s&s
 ( ye>s  to travel to u1 is suffici5tly 
compreh5sive to be treat$ 9 m  detail4  
,radial ,velocities    ,:5 ! #gb-;in*   
telescope 0 9 c\rse ( design &          
con/ruction1  "o ( ! greate/ ne$s 9     
a/ronomical "w 0 increas$ data 9  reg>d 
to ! radial velocities ( ! />s4 ,al?\gh 
! telescope  0 s design$ z to be        
suitable = all k9ds ( obs]vational  "w1 
special att5tion 0 devot$ to !          
spectroscopic end4 ,aft]  consultation )
 ! mo/ prom95t a/ronom]s an obs]v+      
programme  ( ab\t #hjj />s ^: 8prop]0 or
 cross motions across ! sky 7           

accurately kn[n b ^: radial velocities  
_h n be5 det]m9$1  0 prep>$ &           
spectroscopic obs]vations ( ! />s on ?is
  programme 7 comm5c$ z soon z !        
telescope 0 complet$ 9  ,may #aiah4     
,aft] slightly ov] ?ree ye>s' "w1       
obs]vation &  measurem5t 7 complet$ &   
,vol4 ,,ii1 ,no4 #a ( ! obs]vatory      
publications1 8,! ,radial ,velocities ( 
#eid ,/>s10 0 publi%$ e>ly  9 #aibb4 ,z 
hi!rto ! radial velocities ( only ab\t  
#b1jjj />s  _h be5 obta9$1 ?is "w 0 a   
consid]able addition to exi/+  data ab\t
 ! motions ( ! />s & w be ( great use 9 
ext5d+ our k ( ! /ructure & motions ( ! 
univ]se4  ,a second programme ( #a1ejj  
/>s has be5 prep>$ b ow+ to o!r  int]v5+
 obs]vational "w1 n mu* has yet be5 done
 on ?is new  programme4    ,"o ( !      
auxili>y programmes und]tak5 & ne>ly    
complet$ s9ce  ! fir/ programme is !    
det]m9ation ( ! radial velocities ( a  v
 int]e/+ b limit$ class ( />s1 ! highe/ 
temp]ature  />s kn[n1 ! ,o-type />s4 ,! 
radial velocities & o!r  int]e/+ data   

ab\t #ej ( ^! />s h be5 complet$4       
,spectroscopic ,d\ble ,/>s    ,9 !      
measurem5t ( ! radial velocity ( ! #hjj 
/>s on !  fir/ programme x 0 f\nd t 9   
ab\t #ahj />s successive plates  did n  
give con/ant velocities1 ! />s at "o "t 
approa*+  at ano!r rec$+ f u4 ,?is      
ph5om5on is practically c]ta9  pro( t we
 are measur+ ! velocity ( a /> revolv+  
ar\nd an  invisible companion & su* />s 
are g5]ally call$ spectroscopic  b9>ies 
to di/+ui% !m f visual b9>ies :i* c be  
se5  d\ble 9 ! telescope4 ,ov] #bjj     
spectroscopic b9>ies h be5  discov]$ at 
?is obs]vatory z comp>$ ) ab\t #gjj     
discov]$  else:]e1 aga9 a consid]able   
addition4 ,9 ab\t #bj ( ^!  b9>ies1     
obs]vations 7 cont9u$ until ! p]iod (   
revolution1  ! =m ( ! orbit1 ! sep>ation
 ( ! two />s & 9 "s  cases1 _! masses 7 
det]m9$4 ,9 a p>ticul> class (          
spectroscopic b9>ies1 ! eclips+         
v>iables1 :i* all[ f !  comb9ation (    
spectroscopic & photometric measurem5ts 
! absolute  dim5sions to be obta9$1 we 7

 able to det]m9e ! sep>ation (  ! two   
/>s1 _! diamet]s1 d5sities1 masses &    
brightnesses &  ! probable di/ances4    
,su* complete in=mation has be5 obta9$  
"h ab\t sev5 sy/ems1 :ile only sev5 o!r 
sy/ems h be5  det]m9$ else:]e4          
,absolute ,magnitude & ,di/ance    ,a   
new application ( spectroscopic me?ods  
is to ! det]m9ation (  ! total          
brightness ( ! />s z comp>$ ) ! sun & _!
  di/ance or 8spectroscopic p>allax0 z x
 is call$4 ,?is dep5ds n  on ! positions
 b on ! relative int5sity or /r5g? ( !  
l9es  9 ! spectra ( ! />s & has only be5
 develop$ 9 ! la/  ?ree or f\r ye>s4 ,! 
absolute magnitude & spectroscopic      
p>allax  ( ab\t #hjj />s is n[ ne>ly    
complet$ & w soon be publi%$  :ile z a  
side l9e ! radial velocities ( #abe m   
/>s h be5  det]m9$4      ,physical      
,conditions 9 ! ,/>s    ,! spectrographs
 h also be5 us$ by "o memb] ( ! /aff 9  
! det]m9ation ( ! physical & *emical    
conditions 9 /ell>  atmosph]es1 a new & 
difficult problem b "o :i* promises n   

only v valuable additions to our k ( !  
con/itution (  ! />s b may also lead to 
economic applications ( ! greate/       
importance4 ,a new me?od dep5d+ ^u ! use
 ( a w$ge ( d>k  glass has be5 appli$ to
 det]m9+ ! di/ribution ( en]gy 9 !      
diff]5t p>ts ( ! spectrum ( ! />s & to  
measur+ _!  temp]atures1 :ile an        
application ( ! same me?ods to          
individual  l9es may lead to a great    
increase 9 our k ( conditions 9  ! />s4 
,a special inve/igation ( ?ree ( ! high 
temp]ature  ,o-type />s ref]r$ to above 
has prov$ ! exi/5ce 9 ! spectra  ( ^!   
/>s ( l9es pr$ict$ z pres5t f purely    
!oretical  conditions b nev] previ\sly  
id5tifi$ & has ?us rem>kably  v]ifi$ a  
!ory ( ! /ructure ( ! atom4 ,!          
measurem5t ( !  wave l5g?s ( ^! hi!rto  
unkn[n l9es has l$ to an important      
indep5d5t det]m9ation ( ! fundam5tal    
con/ants ( atomic  /ructure & !         
dim5sions ( ! atom & has %[n t ^!       
con/ants & dim5sions are ! same 9 !     
trem5d\s furnaces (  ! />s z 9 our      

t]re/rial laboratories1 a v]ification ( 
!  homog5eity ( matt] & ! uni=mity (    
physical laws ?r\gh\t  ! univ]se4 ,fur!r
 int]e/+ results f ?is inve/igation  are
 ! application ( a new !ory ( ionization
 ) ! probable  relative abundance ( !   
elem5ts to an indep5d5t det]m9ation (  !
 temp]ature ( ^! />s4      ,o!r         
,inve/igations    ,direct photographs h 
be5 made ( "s nebulae & clu/]s b  ?is "w
 is n be+ def9itely foll[$ at pres5t4   
,inve/igations  into ! ph5om5a          
accompany+ "s %ort p]iod b9>ies h be5   
made & into ! behavi\r ( ! two /rong    
calcium l9es ,h & ,k  9 ! spectra ( !   
high temp]ature />s f :i* int]e/+  &    
valuable results are expect$4 ,s9ce !   
obs]vatory comm5c$  "w two bright novae 
or new />s h appe>$1 :i* h be5  fully   
obs]v$ spectroscopically "h & ! results 
discuss$4 ,!  plates ( ! nova 9 ,aquila 
h be5 loan$ to ! obs]vatory at !        
,univ]sity ( ,cambridge1 ,engl&1 = full]
 discussion & analysis4      ,value (   
,a/ronomical ,"w    ,?is brief sket* ( !

 "w ( ! obs]vatory naturally leads to  !
 "q frequ5tly ask$ ( a/ronom]s3--,:at   
use is ! "w  done at obs]vatories & :at 
practical value c a k ( !  />s h 9      
ev]yday life8 ,:ile a/ronomy has obvi\s 
practical  applications to navigation & 
survey+ yet n9e-t5?s ( mod]n            
a/ronomical rese>* is devot$ to ! m or  
less ab/ract "q  ( ! con/itution &      
motion ( ! />s & ! /ructure ( !         
univ]se4 ,inde$ mo/ physical & *emical z
 well z a/ronomical  rese>* is und]tak5 
= ! purpose ( increas+ our k  & (       
inve/igat+ ! secrets & laws ( nature &  
has g5]ally  no direct practical        
economic application4 ,b x is n[ g5]ally
  recogniz$ by ! layman z well z !      
sci5ti/ t )\t ab/ract  !re c be no      
appli$ sci5ce & t all ! great economic &
  indu/rial applications ( sci5ce h _h  
to be prec$$ by !  ab/ract & app>5tly   
non-practical inve/igations ( pure      
sci5ce4  ,! ,great ,w> p]haps made m    
evid5t ?an ev] be=e ! absolute  dep5d5ce
 ( appli$ sci5ce ^u ! unselfi% & ab/ract

 "w (  pure sci5ce4      ,economic      
,value    ,9 view ( pa/ exp]i5ce 9      
sci5ce x w\ld h5ce be a ra%  pr$iction  
to ass]t t ! inve/igation ( ! conditions
 9  di/ant />s c h no practical         
application ^u e>?4 ,x may be  ( int]e/ 
to po9t out "o possible application (   
a/rophysical  rese>*4    ,x is g5]ally  
agre$ t "o ( ! mo/ important economic   
problems ( ! n f> di/ant future w be !  
provision (  s\rces ( en]gy to replace  
our rapidly deplet+ supplies ( coal  &  
oil4 ,x appe>s n[ t ! mo/ probable      
solution ( ?is  problem w consi/ 9 !    
developm5t ( "s me?od = utiliz+  !      
inexhau/ible /ores ( en]gy conta9$ 9 !  
atoms ( matt]4  ,mod]n rese>* on        
conditions 9 ! />s has made x           
practically  c]ta9 t ! enorm\s supply ( 
en]gy1 :i* has be5 radiat$  into space =
 aeons ( "t f ^! bodies1 c only be      
ma9ta9$  undim9i%$ by ! en]gy releas$ by
 ! trans=mation ( atoms  9 ! int]ior ( !
 />s1 :]e conditions ( temp]ature &     
pressure prevail at pres5t unatta9able 9

 t]re/rial laboratories4  ,! mo/ hopeful
 l9e ( attack ^u ?is trem5d\sly         
important  economic problem h5ce seems  
to lie 9 ! sy/ematic a/rophysical       
inve/igation ( conditions 9 ! />s       
supplem5t$ by physical &  *emical       
rese>*es on ! /ructure ( ! atom4        
,e?ical ,value    ,:ile a/ronom]s &     
sci5tific m5 g5]ally fully realize !    
value  ( ! practical applications (     
sci5ce1 _! ma9 purpose is !  se>* = tru?
 & ! ext5sion ( our k ( nature4 ,:ile x 
is possible t inve/igation ( ! />s may h
 imm5se economic  value1 x is c]ta9 t x 
has trem5d\s e?ical value giv+ u a      
cle>] k ( ! laws ( nature & ( our       
relations to !  wond]s ( creation4      
,a/ronomy is ! olde/ & 9 _m respects !  
mo/ important ( ! sci5ces & its /udy1   
?r\gh ! ages has  be5 "o ( ! mo/ elevat+
 influ5ces on human "*4 ,po9c>  has well
 said t if ! e>? _h be5 s cont9u\sly    
cov]$ )  cl\ds t ! heav5ly bodies c\ld n
 be se51 mank9d w\ld /ill  be 9 a       
primitive /ate & "u ! doma9 (           

sup]/ition4 ,! ma9  sup]iority ( mod]n  
ov] anci5t civilization does n consi/ 9 
!  great] abundance ( ! necessities &   
luxuries ( life1 al?\gh  ?is is         
und\bt$ly due prim>ily to sci5tific     
rese>*1 b to !  elevat+ influ5ces ( !   
tru] conceptions ( nature made possible 
by ! ab/ract /udy ( a/ronomy & o!r      
sci5ces4    ,x has be5 truly said t !   
degree ( civilization ( a c\ntry may  be
 judg$ by ! support x gives to ! /udy ( 
a/ronomy4 ,by !  e/abli%m5t & ma9t5ance 
( ! ,dom9ion ,obs]vatory at ,ottawa  & (
 ! ,dom9ion ,a/rophysical ,obs]vatory at
 ,victoria ) !  second l>ge/ telescope 9
 ! _w1 ,canada has a j claim on ?is     
crit]ion to ! fav\rable e/imation ( !   
sci5tific _w4      ,,victoria1 ,b4,c41  
,may1 #aibc4          ,,transcrib]',s   
,,notes3        ,italiciz$ text is      
surr\nd$ by und]scores3 italics4        
,obvi\s typographical errors h be5      
correct$4