Notes. 



415 



To prevent this overlapping and confusion of images, it is 

 necessary to confine each set of rays to one side of the tube and 

 one segment of the field of view. This is accomplished by insert- 

 ing into the draw-tube a removable diaphragm or division plate, 



Fig. 82. 



which extends from the fitting containing the reflector to within 

 an inch or so of the ocular, the tube thereby being divided into 

 two semi-cylindrical sections, each of which transmits rays from a 

 different object, and the image of which will occupy separate 

 segments of the field of view. 



