MIL-DTL-48554B
raise the level of illumination in the room to where the pattern becomes indiscernible.
Close the objective cover and observe that the reticle pattern is again discernible by means
of the internal illumination source.
4.17 Counter illumination. Follow 4.16 to acquire proper dark adaptation. Place a
50% neutral density filter in front of the counters. In the darkened area, visually inspect for
conformance with the requirements of 3.17.2. Remove the filter and repeat the visual
inspection to verify conformance with 3.17.2.
4.18 Cleanliness. Inspection for dirt and foreign particles (classed as dirt) shall be
made from the eyepiece end only. The unit under test shall be subjected to the test
procedures outlined in MIL-PRF-13830 for conformance to requirements outlined in 3.6.1
and 3.6.2.
4.19 Environmental conditions. Unless otherwise specified, requirements 3.5.1
through 3.19 inclusive may be verified after all environmental test procedures of 4.19 have
been completed.
4.19.1 Storage and operating temperatures. The temperature tests of 4.19.1.1 and
4.19.1.2 can be combined into one test procedure and performed as such. All required
inspections are to be performed at the specified temperature ranges. The rate of
temperature change shall not be greater than 6°F per minute to prevent thermal shock.
4.19.1.1 Storage temperature. The telescope, with fresh batteries installed and
stabilized at ambient temperature, shall be placed in a test chamber also stabilized at the
same temperature. The temperature shall then be raised to +160°F ± 5°F and allowed to
soak for a period of not less than 4 hours. While thermally stabilized, the telescope shall be
inspected and will not exhibit any signs of physical damage. Upon meeting this
requirement, the telescope will be returned to the ambient temperature environment of
+60°F to +90°F and subjected to all the required tests of 3.4 through 3.19. Upon meeting
all of the above requirements, the telescope shall be placed in the chamber at -60°F ± 5°F
and soaked for a period of not less than 4 hours. While thermally stabilized, the telescope
shall be inspected and exhibit no signs of physical damage. Upon meeting this
requirement, the telescope shall be returned to the ambient temperature environment of
+60°F to +90°F and shall be subjected to all the required tests of 3.4 through 3.19. All
requirements shall be met.
4.19.1.2 Operating temperature. The telescope, with fresh batteries installed and
stabilized at ambient temperature, shall be placed in a test chamber also stabilized at the
same temperature. The temperature shall then be raised to +145°F ± 5°F and the telescope
shall be allowed to soak for a period of not less than 4 hours. While thermally stabilized,
the telescope shall be subjected to the tests required by 3.13 through 3.15. Upon meeting
the operating requirements, the temperature in the chamber will be lowered to -50°F ± 5°F
and the telescope will be soaked for a period of not less than 4 hours. While thermally
stabilized, the telescope shall be subjected to the tests required by 3.13 through 3.15. All
operating requirements shall be met.
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