GB191321621A - Improvements in Terrestrial Telescopes of Variable Power. - Google Patents

Abstract

21,621. Zeiss, C., [Firm of]. Oct. 4, 1912, [Convention date]. Telescopes.-In variablepower terrestrial telescopes having a collective system, such as II, Figs. 1 and 5, at least a collective member of the collective system is arranged to be transferred from a position in front of the focal plane o f the objective I to a position behind the focal plane. In a form where the distance between the front lens and the rear lens is invariable, as shown in Fig. 5, one member III<a> of the reversing-system III is made movable through a distance that is small compared with the movement of the collective system II, the movements being effected by rotating a divided sleeve a<1>, a<2> with helical grooves in which pins on the non- rotating mounts engage I. Preferably, the transferred part of the collective system has an approximately symmetrical form. In one form, in which the length of the instrument is invariable, when the position of the collective system is such that its front principal plane coincides with the focal plane of the objective, the reversing system inverts the image without changing its size. In a form with an invariable distance between the members of the collective system and providing only two powers, the images presented to the reversing system by the collective system lie in the same plane for the two positions of the collective system.