Topcon Marine Instruments GPT-2000 Manuel D’Utilisation

   17 CHECK AND ADJUSTMENT

17-7

Collimation is required to make the line of sight of the telescope perpendicular to the horizontal axis of 
the instrument, otherwise, it will not be possible to extend a straight line by direct means.

●

1) Set the instrument up with clear 

sights of about 50 to 60meters
(160 to 200 ft.) on both sides of the 
instrument.

2) Level the instrument properly with the 

plate level.

3) Sight Point A at approximately 50 

meters (160 ft.) distance.

4) Loosen the vertical motion clamp 

only, and rotate the telescope 180° or 
200g around the horizontal axis, so 
that the telescope is pointed in the 
opposite direction.

5) Sight Point B, at equal distance as 

Point A and tighten the vertical 
motion clamp.

6) Loosen the horizontal motion clamp 

and rotate the instrument 180° or 
200g around the vertical axis. Fix a 
sight on Point A once more and 
tighten the horizontal motion clamp.

7) Loosen the vertical motion clamp 

only and rotate the telescope 180°
or 200g around the horizontal axis 
once more and fix a sight on Point C, 
which should coincide with previous 
Point B.

8) If Points B and C do not coincide, 

adjust in the following manner.

●

1) Unscrew the cross-hair adjustment section  cover.
2) Find Point D at a point between Points C and B, which should

be equal to 1/4th the distance between Points B and C and 
measured from Point C. This is because the apparent error 
between Points B and C is four times the actual error since
the telescope has been reversed twice during the checking 
operation.

3)Shift the vertical cross-hair line and coincide it with
Point D, by revolving the left and right capstan 
adjustment screws with the adjusting pin.Upon 
completing the adjustment, repeat the checking 
operation once more.
If Points B and C coincide, further adjustment is not 
required. Otherwise ,  repeat the adjustment.

 

 

 

 

Eyepiece

Telescope

 

Capstan
adjustment
screws

Eyepiece

Capstan
adjustment
screws