Palomar Observatory Sky Survey
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Palomar Observatory Sky Survey(POSS) A photographic star atlas of the northern sky and part of the southern sky to a declination of –33°. It was prepared at the Mount Palomar Observatory, California, with the collaboration of the National Geographic Society, using the 48-inch Oschin Schmidt telescope. It was released 1954–58. It consisted of 935 pairs of photographic prints: one of each pair was made from an exposure on a blue-sensitive plate, the other was made from an exposure taken through a red filter. This survey, known as POSS-I, included stars to a limiting magnitude of 21 (20 in the southernmost plate). A second survey of the northern sky, known as POSS-II, was carried out in the 1980s with an upgraded version of the Palomar Oschin Schmidt, using much improved film. Objects four times as faint as those photographed by POSS-I were recorded. Identifications on POSS prints can be made using a set of labeled transparent overlays, prepared at Ohio State University by R. Dixon and published in 1981. The prints from both POSS-I and POSS-II are being converted to computerized digital format and are becoming accessible over the World Wide Web and as part of the Digitized Sky Survey. See also Southern Sky Survey.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006