Surveying - Carpenter's and Builder's Math, Plans, and Specifications - page 220

8. Sight again at the first point and clamp.
9. Again, revolve the telescope vertically by one-half a revolution.
If the line of sight falls on the pin, the telescope is collimated.
If not, drive a new pin on the last sight at the same distance
as before, and drive another pin at one-fourth the distance
between the first pin and the second.

10.

Move the vertical crosshair by means of the capstan-headed
screw and an adjusting pin, until the intersection of the
crosshairs covers the last pin set.

11.

Repeat the operation to be certain of collimation.

Third Adjustment
Adjust the horizontal axis so that the line of collimation will move
in a vertical plane.

1. Level up carefully and sight on a high, well-defined point (such
as a corner of a chimney) and clamp.
2. Slowly move the telescope down until it sights the ground, and
drive a pin there.
3. Unclamp. Revolve the vernier plate one-half of a revolution,
and revolve the telescope vertically one-half of a revolution,
thereby reversing the line of sight.
4. Look again at the high point and clamp.
5. Slowly move the telescope down until it sights the ground. If
the intersection of the crosshairs covers the pin, the horizontal
axis is in adjustment. If not, correct halfway by means of a
support-adjusting screw and the rest of the way by means of
the plate screws.

6.

Repeat the operation, and verify the adjustment.

Fourth Adjustment
Make the line of collimation horizontal when the bubble of the
attached level is centered.

1. Drive two stakes 300 to 400 feet apart, and set up the instru-
ment approximately halfway between these stakes.
2. Level up and take readings on the rod held successively on the
two stakes. The difference between the readings is the differ-
ence of elevation of the stakes.
3. Next, set the transit over one of the stakes, level up, and take
a reading of the rod held on the other stake.