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.
Berkeley Open Cluster Catalogue (Be)
Digitized Sky Survey (DSS)
Atlas of Galactic Nebulae (GN)
Lynds Bright Nebula Catalog (LBN)
Lynds Catalog of Dark Nebulae (LDN)
Morphological Catalogue Of Galaxies (MCG)
Palomar 48 Inch Telescope (P48)
Palomar Globular Clusters (Pal)
Sharpless Catalog (Sh2)
Uppsala General Catalogue (UGC)
Van Den Bergh Reflection Nebula Catalog (vdB)