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   17 CHECK AND ADJUSTMENT

17-8

Adjustment is required to make the line of sight of the optical plummet telescope coincide with the 
vertical axis ( otherwise the vertical axis will not be in the true vertical when the instrument is optically 
plumbed).

●

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.

●

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.

Note:

1

First, loosen the capstan adjustment screw on the side to which the vertical cross-hair 
line must be moved. Then tighten the adjustment 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.

2

Perform  following adjustment after completing above adjustment . Section 17.3.7 
“Adjustment of Vertical Angle 0 Datum”, Section 17.2 “Checking the Optical Axis”.

Note:

First, loosen the capstan adjustment screw on the side to which the center mark must be 
moved. Then tighten the adjustment 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.

Capstan
adjustment
 screws

Eyepiece

Capstan 
adjustment 
screws

Plummet telescope

Half amount of 
displacement

Total amount of 
displacement