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| MIL-T-81333A(0S)
4.5.4.4.2 Test procedure. In all focusing and testing, the particular aperture being observed should be cen-
tered in the fieid of view of the telescope under test and the image observed with the aid of the auxiliary telescope
Focus the telescope under test on the white star for best image as seen through the auxiliary telescope The star
image shall appear round with a sharply defined edge and shall be free from points, flares, rays, fog, haze, and
halos other than the normal diffraction rings. No difference in coloration between one side of the star and the other
shall be seen. Defocus the telescope under test slightly in either direction. The blurred image of the star shall
remain round. Focus the telescope under test successively on the red star, adjusting for best focus as seen through
the auxiliary teiescope and observe whether the blue star is also in focus
4.5.4.4.3 Resolution. The telescope shall be tested for resolution to determine conformance to 3.3.3. The tar-
get for the resolution test shall be of the Foucault resolving power pattern containing horizontal and verticai black
bars on a white field. it shall be brightly illimunated by tungsten light without filters. Variation of target illumination
to obtain opimum resolution is permitted. The auxiliary telescope should have a magnification of not less than
3 nor more than 6 diameters. The telescope under test shall be focused on the target for best image as seen through
the auxiliary telescope.
4.5.4.4.4 Eypiece focus. The eyepiece shall be tasted for proper setting using a diopterscope of at least four
POWer (see 6.4). Motion of the diopterscope eyepiece away from its objective is considered negative and toward
it positive. Focus the diopterscope on a distant target and read the scale introduce diffused light into the objective
of the telescope under test. With the objective of the diopterscope at the exit pupil of the telescope under test,
focus the diopterscioe for clearest image of the reticle of the telescope and again read the scale. The eyepiece
setting is calculated as the reciprocal of this distance in meters.
4.5.5 Environmental tests
4.5.5.1 Shock. The telescope shall be subjected to shock tests in accordance with MIL-S-901 for the grade,
ciassification, and class of equipment specified therein. Prior to shock tests, the position of controls and adjust-
ments shall be recorded. The reticle lamp shall be illuminated during shock tests. After being subjected to shock
test, the telescope shall be deemed acceptable if it shows no damage, controls and adjustments have not appreciably
shifted, and performance as specified herein is not impaired.
4.5.5.2 Vibration. The telescope shall be subjected to Type I environmental vibration tests specified in MiL-
STD-167. Prior to vibration, the position of controls and adjustments shall be recorded. The reticle lamp shall be
illuminated during vibration tests. Upon completion of vibration tests the telescope shall be deemed acceptable
if it shows no damage, controls and adjustments have not appreciably shifted, and performance as specified here-
in is not impaired.
4.5.5.3 Temperate and humidity. The telescope shall be subjected to the temperature and humidity tests
specified in MiL-F-18870 for Class 2 equipment.
4.5.5.4 Enclosure. The telescope shall be charged with dry air to a pressure of 4 psi. Drying and charging proce-
dures should be in accordance with OP 3750. The exact internal air pressure, ambient temperature, and baromet-
ric pressure shall be simultaneously recorded. The air inlet valve shall then be closed to seal the telescope and
the time recorded. The telescope shall then be subjected to the following temperatures in the order listed:
a. Room temperature (approximately 72 F) until stabilized
b. Ambient temperature of +155 F for at least 5 hours
c Room temperature (appoximateiy 72 F) for at least 2 hours
d. Ambient temperature of -20 F for at least 16 hours
e. Room temperature (approximately 72 F) for approximanately 24 hours
During and at the end of the -20 F temperature run of d. above the telescope shall be examined to determine
that no condensation or moisture has collected on the internal surfaces of the telescope and on the surfaces of
optical components At the end of the temperature run of e. above, the telescope internal air pressure ambient
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