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8.5 Checking and Adjusting the Optical Plummet Telescope
Adjustment is required to make the line of sight of the optical plummet tele-
scope coincide with the vertical axis ( otherwise the vertical axis will not be in
the true vertical when the instrument is optically plumbed).
●
Check
ing
1
Coincide the center mark and the point. (See Chapter 2
“PREPARATION FOR MEASUREMENT” .)
2
Rotate the instrument 180° or 200g around the vertical axis and
check the center mark.
If the point is properly centered in the center mark, adjustment is not
required. Otherwise, adjust in the following manner.
●
Adjustment
1
Take off the adjustment section cover of the optical plummet
telescope eyepiece. This will expose four capstan adjustment
screws which should be adjusted with the accessory adjusting pin to
shift the center mark to the point. However, correct only one-half of
the displacement in this manner.
2
Use the leveling screws and coincide the point and center mark.
3
Rotate the instrument 180° or 200g around the vertical axis once
more and check the center mark. If it is coincided to the point, then
further adjustment is not required. Otherwise, repeat the
adjustment.
First, loosen the capstan adjustment screw on the side to
which the center mark must be moved. Then tighten the ad-
justment screw on the opposite side by an equal amount which
will leave the tension of the adjustment screws unchanged.
Revolve in the counterclockwise direction to loosen and in the
clockwise direction to tighten, but revolve as little as possible.
1/2 of
displacement
Capstan
adjustment
screws
Capstan
adjustment
screws
Plummet telescope
Eyepiece
