position of the line of sight through the reticle foresight mark. Any
difference between the recorded positions of the line of sight for each
boresight knob is the amount of backlash. Backlash in each boresight
mechanism shall not exceed the tolerance specified in 18.104.22.168, as measured
on the target.
NOTE: Should overtravel occur during rotation of the boresight
knobs, the test in nullified and shall be repeated.
4.6.-6.15 Eyepiece focus.- A calibrated diopometer conforming to
Drawing A7284901 shall be utilized for measuring the accuracy of the
zero diopter setting of the diopter scale. Set the diopometer objective
scale to zero and adjust the dioptometer "eyepiece for best focus of the
dioptometer reticle. Set the diopter knob of th eelbow assembly eyepiece
to indicate zero diopter. Position the dioptometer at the eyepiece of
the elbow assembly. While viewing through the dioptometer, obtain best
focus of the phosphor grain on the image tube by adjustment of the diop-
tometer objective scale. The phosphor grain of the image tube shall be
in best focus within the tolerance specified in 22.214.171.124 as measured on
the dioptometer objective scale.
126.96.36.199 Diopter movement.- This test shall be performed in con-
junction with 188.8.131.52 to determine compliance with 184.108.40.206.1. Rotate
the diopter adjustment ring from the established best focus of the
target image to its clockwise stop and note the diopter setting on the
scale; then rotate the diopter ring to its counterclockwise stop, note
diopter setting on the scale. The diopter movement shall meet the
requirements specified in 220.127.116.11.1 as measured o the diopter scale of
the elbow assembly.
18.104.22.168 Diopter backlash.- With backlash excluded for direction
of travel, rotate the diopter ring clockwise and obtain best focus of
the phosphor grain on the screen of the image tube. Record the diopter
scale reading. Continue rotation of diopter ring to its stop, then with
backlash included, rotate the knob counterclockwise and obtain best
focus of the phosphor grain on the screen of the image tube without
overtravel. Record the diopter scale reading. The difference between
the first and second recorded scale reading is the amount of backlash in
the diopter movement. Backlash in the diopter movement shall not
exceed the tolerance specified in 22.214.171.124.
NOTE: Should overtravel occur during rotation of the diopter ring
the test is nullified and shall be repeated.
126.96.36.199 Parallelism if image and reticle.- Perform this test
while observing through the elbow assembly eyepiece with the unaided
eye. Position one extremity of the elbow assembly vertical reticle line
coincident to the vertical: target image line. The opposite extremity of
the elbow assembly vertical reticle line shall be within the gate provided
on the target image to be in compliance with 188.8.131.52.
184.108.40.206 Electron image shift.- Observe through the elbow assembly
eyepiece and establish coincidence of the elbow assembly reticle bores
cress and the projected target image crosslines by means of the boresight