Surveying - Carpenter's and Builder's Math, Plans, and Specifications - page 203

Second Adjustment
This is where you set the bubble line in a plane with the bottom
element of the collars.
1.

Unclip the telescope, and clamp the instrument over a pair of
plate screws.

2.

Center the bubble by means of the plate screws.

3.

Carefully (and very slowly) turn the telescope in the collars in
a small arc to the right, then to the left. If the bubble moves
from center, bring it back by means of the azimuth or side
screws.

Third Adjustment
Setting the bubble line parallel to the bottom element of the collars.
1. Unclip the telescope, and clamp the instrument over a pair of
plate screws.
2. Center the bubble by means of the plate screws.
3. Carefully take the telescope up, replacing it carefully in the Ys
in the opposite direction (that is, the objective sighting in the
direction where the eyepiece originally was). If the bubble has
moved, bring it back halfway by means of the altitude or foot
screws of the spirit level and the rest of the way by the plate
screws.
4. Repeat in another direction until the adjustment is satisfactory.
The second relation is established by making the bubble line stay
in the center of the graduation during a complete revolution of the
instrument around its spindle.
Fourth Adjustment
Now, make the axis of the instrument (not of the telescope) vertical.
1. Pin the clips.
2. Clamp and center the bubble over a pair of plate screws.
3. Reverse the telescope over the same pair of plate screws.
4. Bring the bubble halfway back (if it has moved) by means of
the plate screws.

Fifth Adjustment
Again, make the bubble remain centered during a full revolution of
the instrument.
1. Center the bubble.