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|  MIL-T-70521A (AR)
4.7.2.4 Parallelism of reticle and image. perform this test in
conjunction with the test in 4.7.2.1. Position the telescope with
the eyepiece in the vertical position ("zero" rotational position).
Adjust the telescope holding device in azimuth, if necessary, to
position one extremity of the telescope's vertical reticle line
coincident to the target vertical line image. Teh reticle line
shall be parallel to the target vertical line image within the
tolerance specified in 3.4.4, as measured at the other extremity of
the telescope's reticle line with respect to the target image
tolerance marks. Repeat the above test with the telescope shall
meet the requirements of 3.4.4 in each of its 3 indexed positions.
4.7.2.5 Eyepiece focus. A calibrated dioptometer with a
magnificaiton of at least 3 power (3x) and a diopter measuring range
of zero to minus three diopter shall be utilized for measuring the
eyepiece focus of the telescope reticle. Set the dioptometer
objective diopter scale to zero and adjust the dioptometer eyepiece
for best focus of the dioptometer reticle. Position the dioptometer
at the eyepiece of the telescope. observe through the dioptometer,
obtain best focus of the telescope reticle by adjustment of the
dioptometer objective diopter scale. The telescope reticle shall be
in best focus within the tolerance specified in 3.4.5, as measured
on the dioptometer objective diopter scale.
4.7.2.6 Illumination. The reticle illumination test shall be
performed under simulated conditions specified in 3.4.6. The
luminosity test shall be performed in a dark room having a variably
controlled light source. To perform this test, the observer must be
dark adapted by being in a darkened room for a minimum of 15 minutes
before viewing the reticle markings. Prior to performing the test,
place a white matted surface approximately 2 feet from the telescope
window. Perform the test by observing the reticle pattern and
determine that this pattern is clearly discernible by means of the
self-illuminating source in the dark room. Gradually raise the
level of illumination to where the pattern becomes indiscernible.
Center an aperture stop over the objective entrance aperture of the
telescope and observe that the reticle pattern is clearly discern-
ible. The aperture of the stop shall approximate one half (1/2) the
interior diameter of the retainer for the objective lens. Raise the Raise the
ambient level of illumination to 10 foot candles, remove the fixed
stop and observe the reticle pattern. Repeat the above test with a
5O% neutral density filter placed over the viewing end of the tele-
scope. The reticle illumination of the telescope, with and without
the 50% neutral density filter, shall meet the requirements of
3.4.6.
4.8 Workmanship. The telescope shall be subjected to a visual
and tactile examination for evidence of faulty workmanship. The
telescope shall conform to the requirements of 3.6.
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