A-A-52023
daylight hours under normal atmospheric conditions. The target/plate component of CRM shall be mounted on a vertical standard or carrier which will have a base containing clutch bolts designed to mate with the universal tribrach lever or cam-action locking device. The carrier shall contain a level housing and be capable of independent rotation about the vertical axis 360 degrees in both clockwise and counter-clockwise directions. The level housing portion of the carrier shall contain a liquid-filled tubular level vial, marked with permanent graduations at 2mm intervals with a sensitivity of approximately 45 to 75 arc-seconds per graduation. The level vial housing shall be fitted with a mechanism for independent adjustment of the enclosed vial. A means of background illumination of the translucent target plate shall be provided using incandescent lighting powered by either an integrated small battery source or separate tripod mounted battery pack.
Tribrach assembly: The tribrach is a mounting/leveling/centering mechanism which accommodates interchangeability the base assemblies of the target and the theodolite used in the conduct of field operations. The tribrach shall be diecast of corrosion-resistant alloy and be configured with three integral flanges spaced 120 degrees apart. The finish shall visually approximate green 383. The visual matching can be achieved if item is painted in accordance with TT-E-529, matching color chip 24102. Each flange shall accommodate adjustable leveling screws from material conforming to ASTM B 151, UNS 79200, H01 temper. The adjusting nuts and milled leveling knobs shall conform to ASTM B 16, HO2 temper. The leveling screws shall permit leveling of the target when the base plate is not more than 6 degrees out of level. The base of the tribrach shall contain three clutch bolts. The holes shall be centered on the same 120 degree tribrach radials and 1.25 inches (31.75 mm) from the tribrach center point. The tribrach will be connected to a base plate which provides a bearing surface of corrosion-resistant case hardened steel for mounting the tribrach on the tripod head. The center of the base plate shall have 5/8-11 UNC-2B nut for mating to the tripod head. A means of providing equal downward tension perpendicular to each radial arm of the base plate shall be accomplished using a tempered plate spring, either plated or treated to resist corrosion and attached to the base plate with a nut and lock screw. A circular level shall be in a metal housing as part of one of the tribrach flange castings. The level contained therein shall be adjustable and have sensitivity of between 7-13 arc-minutes per 2mm graduation. The center of the vial shall be etched with a circle 2mm in diameter. A means of rapidly disengaging the target/theodolite base from the tribrach assembly shall be provided by a locking device controlled by a lever or cam action knob composed of material conforming to ASTM B 584, UNS C86400 or C86700. The locking plate motion shall secure the clutch bolts of the target base with an error of centering not to exceed 0.002 inch (0.5 mm). An optical plumbing device shall be affixed to the tribrach. The optics shall provide a clear image of the reticle and objective target throughout an operating range of 3 feet (0.914m) to not less than 110 feet (33.5m). The reticle shall be
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