Note: USNO-A2.0 contains 526,280,881 sources, and is based on a re-reduction of the Precision Measuring Machine (PMM) scans from POSS-I O and E plates (>=-18°) and SRC-J and ESO-R plates (<=-20°). USNO-A2.0 was created by Dave Monet () and collaborators at Flagstaff Station, U.S. Naval Observatory.
The major difference between USNO-A2.0 and its previous version USNO-A1.0 is that A1.0 used the Guide Star Catalog as its reference frame whereas A2.0 uses the ICRF as realized by the USNO ACT catalog (Urban et al. 1997). The VizieR search engine uses an on-line compressed version (3.6Gbytes) which was generated at CDS.

I/252/out Post annotation

The USNO-A2.0 Catalogue (Monet+ 1998) ReadMe+ftp metaI/252/out The Full Catalogue (526280881 rows) (Note)

Note: The USNO-B Catalog presents positions, proper motions, magnitudes un blue, red and infrared, as well as star/galaxy estimators for 1,045,175,762 objects derived from 3,648,832,040 separate observations. The data were taken from scans of 7,435 Schmidt plates taken from various sky surveys during the last 50 years.
USNO-B1.0 catalog was created by Dave Monet and collaborators at http://www.nofs.navy.mil/data/fchpix/
Note that the star/galaxy estimators may be mixed up in dense regions.

I/284/out Post annotation

The USNO-B1.0 Catalog (Monet+ 2003) ReadMe+ftp 2003AJ....125..984M metaI/284/out The Whole-Sky USNO-B1.0 Catalog of 1,045,913,669 sources (1045175762 rows)

Note: The construction of the GSC-II is still in progress: this version has no proper motions, and the magnitude limits are 18.5 in F (red) and 19.5 in J (blue). The data are copyrighted, check the data use Policy.

I/271/out Post annotation

The GSC 2.2 Catalogue (STScI, 2001) ReadMe+ftp metaI/271/out The Full GSC2.2.1 Catalogue (455851237 objects) (455851237 rows)

Note: This version of the GSC-II has no proper motions, but the limits on brightness which existed on GSC2.2 (F<18.5, B_j<19.5) were removed.

I/305/out Post annotation

The Guide Star Catalog, Version 2.3.2 (GSC2.3) (STScI, 2006) ReadMe+ftp 2008AJ....136..735L metaI/305/out The Full GSC2.3.2 Catalogue (945592683 objects) (945592683 rows)

I/353/gsc242 Post annotation

The Guide Star Catalog, Version 2.4.2 (GSC2.4.2) (STScI, 2020) ReadMe+ftp 2008AJ....136..735L metaI/353/gsc242 Guide Star Catalogue, Version 2.4.2 (original column names in green) (3485671481 rows)