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.
Note: Note that the J2000 coordinates are not part of the original catalogue, they were computed from dRAs and dDEs, or from the (rho,theta); their accuracy can be low.
Note: the J2000 coordinates are not part of the original catalogue; their accuracy can be low, see the CooFlag column
Note: More recent versions available: UCAC3 (I/315) and UCAC4 (I/322); see also the UCAC home page at http://ad.usno.navy.mil/ucac/
Note: The Naval Observatory Merged Astrometric Dataset (NOMAD) contains astrometric and photometric data for over 1 billion stars derived from the Hipparcos (I/239), Tycho-2 (I/259), UCAC2 (I/289), and USNO-B1.0 (I/284) catalogs for astrometry and optical photometry, supplemented by 2MASS (II/246) near-infrared photometry. An efficient remote query program findnomad1 is available in the cdsclient package, for Unix/Linux platforms
Note: see the UCAC4 document, and the the fix for high proper motion stars. The UCAC home page is available at http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/ucac. Please acknowledge the usage of the UCAC4
Note:
Note: Zone -40/+50deg
(original column names in green) (1692919135 rows)
(original column names in green) (1811709771 rows)
Note: Many errors detected in the positions given in the catalogue, especially in the sign of the declination in the zones -1°<δ<+1°
Note: Errors found in the Final IUE Merged log are reported in the file errata.htx
Note: See also the DENIS home page
Note: The column expnum provides an access to details on the exposures, and a link to the Preview and Retrieval System via the CADC
Note: Details of surveyed literature
