MIL-DTL-48558C
telescope reticle orientation to the target and compare it to the reticle orientation recorded
prior to vibration testing. The observed change in reticle orientation shall be within the
limits stated in 3.6.
4.7 Sealing. Accuracy of the test equipment shall be equal to or exceed the
accuracies depicted on Pressure Tester Two Station Drawing 8565556. Prior to the start
of the test, secure the poppet valve in a closed position and set the diopter adjustment to +3.
Pressurize the telescope with dry nitrogen to a minimum of 5 psig and then remove the
pressure source. Observe interior pressure of telescope. After a period of at least 1 hour,
observe the interior pressure of the telescope and compare with starting pressure. Any
observed change in pressure shall be within the limits stated in 3.7.
4.8 Purging. Accuracy of the test equipment shall be equal to or exceed the
accuracies depicted on Pressure Tester Two Station Drawing 8565556. Connect the test
equipment to the purging valve of the telescope. Adjust the dry nitrogen pressure to 6.00 ±
0.25 psig. The pressure is to remain constant until the dew point of the emergent gas is no
higher than -25 °F. Purging apparatus shall then be removed and the relief valve shall
reseat and maintain an internal pressure within the limits stated in 3.8.
4.9 Optical.
4.9.1 Parallax. This test shall be performed with the telescope positioned as stated
in 4.4. Set the collimator projector to 125 meters. The 20 mil reticle graduation of the
telescope will establish the geometric axis. Observe any apparent movement between the
intersecting point of the telescope s boresight cross and the tolerance block of the target
reticle s horizontal and vertical lines. Any apparent movement between these two points
when the inspector s head is moved up and down or from side to side is considered
parallax. The amount of parallax shall not exceed the limits specified in 3.9.1. Repeat the
above test with the collimator projector set to infinity.
4.9.2 Reticle accuracy. This test shall be performed with the telescope positioned
as stated in 4.4. The telescope shall be unlocked in the adapter and the zero range
graduation of the reticle placed in coincidence with the corresponding line of the target
reticle by means of shimming the unit in the fixture. When coincidence has been
established, observe the position of the 60 mil reticle line with respect to the limit lines of
the target reticle. The angular separation between the 0 mil and the 60 mil graduations
shall be within the limits specified in 3.9.2.
4.9.3 Parallelism of reticle and image. This test shall be performed with the
telescope positioned as stated in 4.4. Sight through the telescope and observe that the 20
mil horizontal line is in coincidence with the horizontal target reticle line at the short
vertical line. Parallelism of the telescope s 20 mil horizontal reticle line shall not exceed
the 30 minute mark on the target reticle as per 3.9.3. This test may be performed at the
same time as 4.9.2.
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