USNO-A1.0 contains 488,006,860 sources, and was compiled from the blue/red overlaps of the detection lists generated from scans of POSS-I O and E plates (>=-30°) and SRC-J and ESO-R plates (<=-35°). USNO-A1.0 was created by Dave Monet (dgm@nofs.navy.mil) and collaborators at Flagstaff Station, U.S. Naval Observatory; it is superseded by the new PMM-USNO-A2.0 version.
The VizieR search engine uses an on-line compressed version (3.4Gbytes) which was generated at CDS.