smoothly, they may be cross-threaded or dirty. Do not
force them if you encounter resistance; instead, back
off, and, after checking to see that they are clean,
square up the instrument, and then try again gently.
Screw the head nut up firmly, but not too tightly.
Screwing it too tightly causes eventual wearing of the
threads and makes unthreading difficult. After you
have attached the instrument, thrust the leg tips into
the ground far enough to ensure that each leg has
stable support, taking care to maintain the footplate as
near level as possible. With the instrument mounted
and the legs securely positioned in the soil, the
thumbscrews at the top of each leg should be firmly
tightened to prevent any possible movement.
Quite frequently, the Builder must set up the
instrument on a hard, smooth surface, such as a
concrete pavement. Therefore, steps must be taken to
prevent the legs from spreading. Figure 5-5 shows
Figure 5-5.Methods of preventing tripod legs from
two good ways of doing this. In view A, the tips of
the legs are inserted in joints in the pavement. In view
B, the tips are held by a wooden floor triangle.
LEVELING A LEVEL
To function accurately, the level must provide a
line of sight that is perfectly horizontal in any
direction the telescope is trained. To ensure this, you
must level the instrument as discussed in the next
When the tripod and instrument are first set up,
the footplate should be made as nearly level as
Next, train the telescope over a pair of
diagonally opposite leveling screws, and clamp it in
that position. Then, manipulate the leveling thumb-
screws, as shown in figure 5-6, to bring the bubble in
the level vial exactly into the marked center position.
The thumbscrews are manipulated by simul-
taneously turning them in opposite directions, which
shortens one spider leg (threaded member running
through the thumbscrew) while it lengthens the other.
It is helpful to remember that the level vial bubble will
move in the same direction that your left thumb
moves while you rotate the thumbscrews. In other
words, when your left thumb pushes the thumbscrew
clockwise, the bubble will move towards your left
hand; when you turn the left thumbscrew counter-
clockwise, the bubble moves toward your right hand.
After leveling the telescope over one pair of
screws, train it over the other pair and repeat the
process. As a check, set the telescope in all four
possible positions and be sure that the bubble centers
exactly in each.
Various techniques for using the level will
develop with experience; however, in this section we
will only discuss the techniques that we believe are
essential to the Builder rating.
Figure 5-6.Manipulating leveling thumbscrews.