A photographic survey of the sky from the north celestial pole to declination −33°, made using the 1.2-m Oschin Schmidt Telescope at Palomar Observatory, California. The original survey, undertaken 1949–56, consists of 936 pairs of plates 0.355 m square, each pair consisting of one plate sensitive to blue light and one to red light. The field of view of each plate is 6°.5. It was financed by the National Geographic Society. A second survey, POSS II, was made in 1985–2000 from the north celestial pole to the equator, using modern photographic plates. It consists of 897 fields in blue, red, and near infrared light, with greater overlap between fields than the original survey. A digitized version, DPOSS, is now available.

http://gsss.stsci.edu/SkySurveys/SkySurveys.htm Information and data retrieval page.