An improved method of optical tooling for the determination of angular alignment of randomly oriented multicomponent systems is described. The method was developed for alignment of the Orbiting Astronomical Observatory. A test object is mounted on a precision rotary table and viewed in autocollimation by a first-order theodolite. Azimuth and elevation readings from subject mirrors and relay mirrors, and azimuth readings from a dihedral mirror reference system are transformed into test object coordinates of roll, pitch, and yaw by a computer program. The program uses matrix optics methods. Errors are discussed.
A fixed direction to which angles measured by autocollimators can be referred is essential in many cases which involve precision measurement of angles. The normal to a mercury surface affords such a standard direction, since the normal is along the local gravity vector and the deviations of the local gravity vector about the direction of the earth center are within the limits of accuracy of most measurements. The high reflectance of the mercury surface makes it specially suitable for use with autocollimators. It has been shown that the loss of reflectance due to ripples which damp out too slowly, and oxidation which progresses with exposure to air, can be eliminated by pouring a film of transparent, highly viscous oil over the mercury.
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