Topcon GPT-8000 Series, Instruction Manual

Page: 109 / 145

9 CHECK AND ADJUSTMENT
9-6
9.3.3 Adjustment of the Vertical Cross-hair
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 vertically running lines).
•Check
1) Set the instrument on 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.).
3) Next swing the telescope vertically using the jog/shuttle, 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, adjustment is required in the reticle plate.
•Adjustment
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.
Eyepiece section
attachment screws
Eyepiece section
attachment screws
Eyepiece
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 9.3.4 “Collimation of the Instrument” , Section 9.4 “Adjustment of Compensation
Systematic Error of Instrument” and Section 9.8 “Inspection and Adjustment of Optic Axis for
Auto -Tracking (GPT-8000A Series)” .