e. Perform the daily preventive maintenance
services (par. 29).
f. Refer to figure 25 and level the theodolite.
Warning
Severe eye damage can result from
performing observations against
direct sunlight without utilizing the
telescope sunglass.
g. Focus the telescope as follows:
(1) Direct the telescope toward a uniformly
light background. Turn the diopter ring on the telescope
eyepiece (fig. 2) until the crosslines are sharp and
black.
Note
Observe the setting on the diopter
ring (fig. 2). This setting will remain
constant for the same observer but
will vary for other observers.
(2) Turn the telescope focusing tube (fig. 4)
to bring into view a clear image of the object being
sighted.
h. The horizontal and vertical circle reading scales
are both observed through the microscope eyepiece (fig.
horizontal position, the horizontal circle image appears
in the upper window. When the inverter knob is turned
with the rib in the vertical position, the vertical circle
image appears in the lower window. Simultaneously
with either of the circle images, the image of the
seconds scale is always visible in the lower window.
Figure 19. Plate level, adjustment.
18. Operation in Extreme Cold (Below 0F.)
With proper precautions and servicing, the
17. Theodolite Operation
theodolite can be used in extreme cold. Its use is
a. Set up the theodolite on the tripod (par. 9).
limited only by the endurance of operating personnel
and conditions affecting visibility. The theodolite should
b. If necessary, install the illumination system (par.
be kept out-of-doors or in unheated buildings for short
periods of nonuse. Extreme temperature changes will
Note
induce internal stresses affecting accuracy and lenses
To operate the illumination system,
and prisms may become fogged. Theodolites to be
position the rheostat knob until
used under conditions of extreme cold should be
desired brilliance is obtained. Place
cleaned and all lubricants removed before being used.
the hand light switch in the ON
Snowfall, winds, and refraction of light are some of the
position.
conditions encountered at low temperatures.
c. Install the eyepiece prisms as necessary (par.
Caution
d. Install the telescope eyepiece or telescope
Avoid subjecting the theodolite to
eyepiece prism sunglass as necessary (par. 49).
sudden changes in temperature.
19. Operation in Extreme Heat
Operation of the theodolite in extreme heat and
under the direct rays of the sun can cause
AGO 5078A 26
