projection ray hy 
| 
owing the same li 
/ 
t 2 gimbal axes, 0 
e and another beli 
sents the projet 
gimbal axis is abit 
the photo point, I? 
bal axes on the ji 
  
       
     
    
    
   
   
  
  
   
    
    
   
     
   
    
    
   
  
  
  
  
    
Above projection centre (a): 
jY — —óy 
c Öy 7 
0Y = —n dy 
dX = —n ôx. 
Below projection centre (b): 
  
0X = 0x 
  
oY = Jy. 
Fig. 6 
[, Effect on the projection. 
11, Total effect. 
Asuming the primary and secondary rotation axis have in all gimbal axes the same 
ius, we then get the total projection error due to errors in the different gimbal 
yis applying equations (1): 
1 
Y» [ee (n * 1) —e;*^ n t e,^] 1 — [e,* (n t 1) —e,* n t eh] 
A —-.B 
€ 15 
4- [ee (n t 1) — e;3 n t e,»] —- 
2 NEC A ED 
M= [e,c(n + 1) —e;?n + e,”] (2) 
— [e£ (n t 1) — e;2 n t ej^] 
e M —— 
t [eg* (n t 1) — e33 n t e,"^] 
  
As to the adjustment of the different terms, the following should be considered: 
Z 
A (an be eliminated by adjusting one gimbal axis, but for only one value of n — ui 
5A constant shift, will be eliminated when centering the plate holder, but for only one 
alue of n =— ; 
value of n f 
(Alteady eliminated with term A; 
ln be eliminated by adjusting one gimbal axis, but for only one value of n — f ; 
LAs term B; 
I, Can be eliminated by adjusting only one gimbal axis, but for one value of n = f 
LZ Discussion of the different errors separately. 
I Primary and secondary axis do not intersect. 
Sistitution of €; = Ü and e, — 0 in equations (2) gives 
oy = 0 
9A — [ee (n T 1) — e4à3 n * e']. 
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