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BELL SYSTEM TECHNICAL JOURNAL 



These points, in the conoscope field, being of equal phase are parts of the 

 same ring, and if matched to a pair of reticule lines, the optic axis is off their 

 center line by an angle e, where 



e = 



ai — a2 



If the separation of the reticule lines corresponds to an angle 2d, we see 

 that 



, _ ai + «2 



Fig. 2.41 — Off center cross hairs 

 so that 



ai = d -]- e and a2 = d — e 



The reading of the dial will be, at this match 



i? = i(5 + «2 + 5 - a2) = 5 - 



«1 -~ (X2 



Hence we have 



sm(d + g) ^ / cosjR - d) 

 sm(d - e) y cosIr + d) 



(2.12) 



