Operating Details

i l l u m i n a t i o n system during nighttime operation of

(5) Place the theodolite (1, fig. 2-4) on the

t h e theodolite (para 2-30). The scale readings are

tripod (2) so that the illumination mirror assembly

obtained during nighttime operation by lighting the

(6, fig. 1-2) will receive adequate light for good

vertical and horizontal circles with the illumination

operation. Secure the instrument loosely to the

system (para 2-25).

t r i p o d with the bridge screw.

(2) The illumination system, when installed,

( 6 ) Carefully move the instrument around the

illuminates both circles, plate level, collimation

tripod head until the point of the plumb bob (4, fig.

l e v e l , and the telescope reticle.

2 - 4 ) is centered exactly over the station point (5).

( 3 ) If the circular compass is used, a suitable

Tighten the instrument to the tripod head with the

n o n m a g n e t i c outside light source must be used to

bridge screw, making sure the plumb bob point

o b t a i n- compass azimuth readings. The operator

s t a y s centered over the station point.

should not attempt to use the hand lamp, since

2-26. Operating Details

magnetic errors may result from the close proximity

a. Daytime Operations.

of the hand lamp to the compass.

( 1 ) During periods of operation when natural

c. Adjustments.

light is available, the illumination mirror, diagonal

(1) Tripod.

eyepieces, s u n g l a s s e s , a n d c i r c u l a r c o m p a s s a r e

(1)

Test

all

wood

screws

for

firm

in-

used according to the degree of light and the

stallation. See that no play exists at the junction of

o p e r a t i n g conditions. Telescope sightings and scale

the wood and metal parts. Be sure that the tripod

readings through small vertical angles from the

h e a d is not bent, burred, or scored. The clamping

horizontal are sighted through the conventional

screws under the head must be tight enough to hold

e y e p i e c e s (1 and 3, fig. 1-4). Large vertical angles

t h e tripod legs in position when the legs are ex-

u p t o 2 5 from the zenith are sighted through the

t e n d e d and about 2 feet apart.

diagonal

eyepiece

prisms.

The

sunglasses

are

(b) The wing screws on the tripod legs must

p r o v i d e d with the instrument for zenith sightings

turn

freely when loose and be kept properly

w i t h the telescope. T h e c o m p a s s i s n o r m a l l y i n -

l u b r i c a t e d to permit easy hand tightening. When

s t a l l e d on the alidade during daylight operation.

the wing screws are tightened, be sure that the

However, the compass may be installed (c (10)

e x t e n s i o n legs clamp securely to the upper tripod

below) and used during either daytime or nighttime

legs. When the wing screws are loose, the extension

operations.

legs should slide easily and smoothly in the grooves

(2) When operating the instrument in sub-

i n the upper legs.

t e r r a n e a n areas or under low light conditions, the

(2) F o o t s c r e w s . The foot screws (9, fig. 1-1)

i l l u m i n a t i o n system must be installed (para 2-30).

m u s t turn smoothly and with moderate ease, but

(3) Always turn the alidade in a clockwise

w i t h o u t backlash. Turning the foot screw adjusting

direction during angular measurements to attain

screw (10, fig. 1-2) with an adjusting pin (4, fig. 2-

maximum accuracy. This rule applies whether

7) increases or decreases the pressure exerted on the

measuring from left to right, or from right to left.

foot screw body. This pressure determines the ease

b. Nighttime Operation.

with which the foot screw knob can be turned.

(1) The operator must instali and use the

2-8