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Parallelism of image and reticle |
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|  MIL-T-60895(MU)
of sight to the position observed in 4.7.2.1.2. All readings are to be
within the limits outlined in 3.7.2.
4.7.2.1.5 Parallelism of image and reticle. - With the panoramic
telescope positioned as outlined in 4.7.1, align one end of the instruments
vertical reticle line to the projector collimator's vertical reticle line
and observe where the opposite end of the panoramic telescope vertical
reticle line falls with respect to the projector collimator vertical reticle
line. Both lines must coincide within the limits specified in 3.7.3. Repeat
this procedure with elbow assembly against each of the extreme stops. Also
repeat this procedure at approximately eight different azimuth settings in
6400 mils of rotation. Return the line of sight to the projector collima-
tor's target line after each selected azimuth setting by rotating the
azimuth fixture plate an equal amount in the opposite direction. All
check points are to be within the limits outlined in 3.7.3.
4.7.2.1.6 Eyepiece focus. - This test is to be accomplished by
placing a white background in front of the panoramic telescope window.
Eyepiece focus is to be measured using a 3 power dioptometer conforming to
the accuracies depicted on Drawing 7680631. Adjust the dioptorneter eye-
piece assembly to the dioptometer's reticle until a clear sharp image
appears on the dioptometers optical axis. Next dircet the dioptometers
line of sight toward a 500 feet distant target such as a smoke stack, edge
of a building, or some other well defined target image. Adjust the
objective assembly until parallax is removed and set the diopter scale to
zero. Parallax is defined as any apparent movement between the reticle and
target image when the head is moved from side to side or up and down.
Align the dioptometers optical axis to the panoramic telescope optical
axis and obtain a clear sharp image of the panoramic telescope reticle on
the optical axis. Make all measurements on the dioptometer by adjusting
the objsective assembly. Any and all adjustments to be within the limits
of 3.7.4.
4.7.2.1.7 Parallax. - Using the set-up outlined in 4.7.1, parallax
will be tested after the distances specified in 3.7.9 has been set into
the projector collimator. The test is performed by aligning a reticle
line or mark near or on the optical axis of the telescope under test to
a similar line or mark on the projector collimator reticle. There shall
be no apparent movement beyond the limits of 3.7.5 between the selected
lines or mark when the observer moves his head from side to side or up
and down. Reticle displacement shall not exceed the limits outlined in
3.7.5. Use the thickness of the reticle line to measure apparent movement.
4.7.2.1.8 Reticle accuracy. - Reticle accuracy may be assured by
aligning the intersecting point of the panoramic telescopes vertical and
horizontal reticle line to the corresponding intersecting reticle lines of
the projector collimator. Adjustments may be made by means of the panoramic
telescope's azimuth and elevating mechanisms. When coincidence has been
established, observe where the 80 mil graduations of the panoramic telescope's
horizontal reticle line falls with respect to the corresponding reticle line
of the projector collimator. The coincide within the limits of the
reticle tolerance mark to assure compliance with 3.7.7.
12.
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