The catalog contains the coordinate of the plate centers forming the Second Epoch Palomar Oschin Schmidt Sky Survey (POSS-II), observed between 1985 and 2000, and covering the Northern sky. The survey was operated by the California Institute of Technology (CalTech) with funds from the National Science Foundation (NSF), the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman Kodak Corporation. The file "poss2.dat" was actually created from a merge of the UKST Plate Catalogue (Royal Obs. Edinburgh) and the POSS2 Photographic Survey Plate Logs (Naval Observatory)