International Correspondence Schools · Scranton, Pa. : The Colliery engineer co. · leaf 34
of collimation. The cross-hairs are fastened to a thick brass ring placedwithin the telescope and held in position by capstan headed screws. Fig.200, let into this ring.They are commonlyplaced at right angles toeach other, the one beingvertical and the otherhorizontal. The ring,together with the… … Fig. 200. 1226. Focusing the Telescope.—The movement ofthe object glass is effected by a milled headed screw U,shown in Fig. 258. This screw moves the object glass outor in, according as the object is nearer or further from theinstrument. The eye-piece is focused upon the cross-hairsby a similar…
Railroad engineering
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