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   17 CHECK AND ADJUSTMENT

17-6

Adjustment is required if the vertical cross-hair is not in a place perpendicular to the horizontal axis of 
the telescope ( since it must be possible to use any point on the hair for measuring horizontal angles or 
running lines).

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1) Set the instrument up the tripod and carefully level it.
2) Sight the cross-hairs on a well defined Point A at a distance of, at least, 50 meters  (160ft.) and 

clamp  horizontal motion.

3) Next swing the telescope vertically using the vertical tangent screw, and check whether the point 

travels along the length of the vertical cross-hair.

4) If the point appears to move continuously on the hair, the vertical cross-hair lies in a plane 

perpendicular to the horizontal axis ( and adjustment is not required ).

5) However, if the point appears  to be displaced from the vertical cross-hair, as the telescope is 

swung vertically, then proceed with the following adjustment.

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1) Unscrew the cross-hair adjustment section cover, by revolving it in the counterclockwise direction, 

and take it off. This will expose four eyepiece section attachment screws.

2) Loosen all four attachment screws slightly with the accessory screw-drive (while taking note of the 

number of revolutions).
Then revolve the eyepiece section so that the vertical cross-hair coincides to Point A’.
Finally, re-tighten the four screws by the amount that they were loosened.

3) Check once more and if the point travels the entire length of the vertical cross-hair, further 

adjustment is not required.

Note:

Perform following adjustment after completing the above adjustment .
Section 17.3.4 “Collimation of the Instrument”, Section 17.3.7 “Adjustment of Vertical Angle 0 
Datum”. 

Eyepiece section 
attachment screws

Eyepiece section 

attachment screws

Eyepiece