From Fig. 14 : x = (h +Ah) tan (z), (105) 
Ah sin (z), Ah sin (=), cos (a), 
  
  
and A = ~ (106) 
a 8 h 
In [13] an expression for x is published, which may be written as: 
tan (z), iy n 7n | 
=  — —— BH 
x -hten (z), + 5 x f = (107) 
cos (2), H p 
For optical frequencies n is usually € 1.0005 but» 1 and we may therefore 
write for (10T) 
H 
to 
tan (a), 
x = h tan (z) + (n; *" nJ)dH (108) 
cos (2), , P 
  
By comparing (105) with (108) it follows from (106): 
tan (2), Ho 
a, TR § (a, T ny) a | (109) 
H 
a 
Due to the linear relationship between temperature and height, (101), we may 
write with the notation in Figure 14 and formula (104) : 
  
  
  
A tan (z), To : | 
ML. f (ny - nj) dT (110) 
| T 
| & 
| From (103): 
| | T a-l 
| na = 1 + a (5) 
| > 
i n =1+0 (E) ni 
In p oT 
li = 9 m a-1 &-l 
a ; a 4 t. ! 
I = . 2 8-1 a-l,  . 08 ( = 
| e nne d ore ema m aem) ] a» 
il 0 0 : 
li 66 
  
xum — 2