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in astronomy, an instrument for measuring the rectangular coordinates of celestial objects on astrophotographs. Coordinate-measuring machines were first used in the late 19th century as photographic astrometry developed.
It is possible to compute the celestial coordinates of the object under study on the astrophotograph by using the machine to measure the rectangular coordinates of the images of several reference stars with known celestial coordinates and the coordinates of the object. Coordinate-measuring machines are designed to measure one coordinate or two mutually perpendicular coordinates. Semiautomatic coordinate-measuring machines were developed in the 1960’s in which the fixing onto the objects to be measured is done by the experimenter and the reading is taken automatically and recorded on punched card or punched tape. In 1970, British engineers built the first industrial automatic coordinate-measuring machine (a photoelectric measuring machine). When integrated with a computer, this machine makes it possible to automate completely the measurement process; the entire system is called Galaxy. The accuracy of measurements done by modern coordinate-measuring machines after investigation and consideration of all instrument errors is ±0.5 μ. In the USSR, industrial production of coordinate-measuring machines was begun in the 1930’s at the Leningrad Optical Machine Plant. The semiautomatic coordinate-measuring machine manufactured by the Carl Zeiss Company (German Democratic Republic) is common.
E. A. IUROV