The Palomar Observatory Sky Survey (POSS, Palomar Observatory Sky Survey I, POSS-I, National Geographic Society-Palomar Observatory Sky Survey, or NGS-POSS) is a set of photographic plates taken in the 1950s with the Palomar 48 Inch Telescope at the Palomar Observatory. A number of Catalogs result from inspecting them for objects of interest.
The Second Palomar Observatory Sky Survey (aka Palomar Observer Sky Survey II or POSS-II) is a repeat done in the 1980s and 1990s with the same telescope but with technological upgrades. The Palomar Digital Sky Survey (DPOSS) is a digitization of the POSS-II photographic plates.
Digitized Sky Survey (DSS)
Lynds Catalog of Dark Nebulae (LDN)
Morphological Catalogue Of Galaxies (MCG)
Palomar 48 Inch Telescope (P48)
Uppsala General Catalogue (UGC)