The National Geographic Society – Palomar Observatory Sky Survey (NGS-POSS, or just POSS, also POSS I) was a major astronomical survey, that took almost 2,000 photographic plates of the night sky. It was conducted at Palomar Observatory, California, United States, and completed by the end of 1958.A. G. Wilson, Trans. I.A.U. 8, 335–336 (1952);R. L. Minkowski & G. O. Abell, in Basic Astronomical Data: Stars and Stellar Systems, edited by K. A. Strand (University of Chicago Press, Chicago, IL, 1968), Appendix II, p. 481–487.
