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.

Full	_r arcsec	_RAJ2000 "h:m:s"	_DEJ2000 "d:m:s"	USNO-A2.0	RAJ2000 deg	DEJ2000 deg	ACTflag	Mflag	Bmag mag	Rmag mag	Epoch yr
1	1.379	21 49 34.65888	-22 05 12.5016	0675-36659027	327.394412	-22.086806			19.5	18.0	1983.078

%0a%0a%3cP%3e%0a%3cFONT%20SIZE=%27-1%27%3e%3cEM%3e%3cFONT%20COLOR=%27#0000FF%27>%3cB%3eNote:%20The%20%3cB%3eUSNO-B%20Catalog%20presents%20positions,%20proper%20motions,%20%0amagnitudes%20un%20blue,%20red%20and%20infrared,%20as%20well%20as%20star/galaxy%20estimators%0afor%201,045,175,762%20objects%20derived%20from%203,648,832,040%20separate%20observations.%0aThe%20data%20were%20taken%20from%20scans%20of%207,435%20Schmidt%20plates%0ataken%20from%20various%20sky%20surveys%20during%20the%20last%2050%20years.%3cBR%3e%0aUSNO-B1.0%20catalog%20was%20created%20by%20Dave%20Monet%20and%20collaborators%0aat%20http://www.nofs.navy.mil/data/fchpix/%20%3cBR%3e%0a%3cB%3e%3cFONT%20COLOR=%27#EE0000%27>%20Note%20that%20the%20star/galaxy%20estimators%20may%20be%20mixed%20up%0a%20in%20dense%20regions.%0a%3cP%3e%0a

Full	_r arcsec	_RAJ2000 "h:m:s"	_DEJ2000 "d:m:s"	USNO-B1.0	RAJ2000 deg	DEJ2000 deg	e_RAJ2000 mas	e_DEJ2000 mas	Epoch yr	pmRA mas/yr	pmDE mas/yr	Ndet	B1mag mag	R1mag mag	B2mag mag	R2mag mag	Imag mag
1	1.531	21 49 34.66008	-22 05 12.3432	0679-1043384	327.394417	-22.086762	247	213	1975.4	0	0	3		18.77	20.50	19.03
2	2.710	21 49 34.75080	-22 05 11.7816	0679-1043385	327.394795	-22.086606	999	554	1972.9	0	0	2		18.96		20.33

%0a%0a%3cP%3e%0a%3cFONT%20SIZE=%27-1%27%3e%3cEM%3e%3cFONT%20COLOR=%27#0000FF%27>%3cB%3eNote:%20The%20Naval%20Observatory%20Merged%20Astrometric%20Dataset%20%28NOMAD%29%20contains%0aastrometric%20and%20photometric%20data%20for%20over%201%20billion%20stars%20derived%20from%0athe%20Hipparcos%20%28I/239%29,%20Tycho-2%20%28I/259%29,%20UCAC2%20%28I/289%29,%20and%20USNO-B1.0%0a%28I/284%29%20catalogs%20for%20astrometry%20and%20optical%20photometry,%20supplemented%0aby%202MASS%20%28II/246%29%20near-infrared%20photometry.%3cBR%3e%0a%3cFONT%20SIZE=%27-1%27%3eAn%20efficient%20remote%20query%20program%20%3cB%3efindnomad1%20is%0aavailable%20in%20the%20cdsclient%20%0apackage,%20for%20Unix/Linux%20platforms%0a%3cP%3e%0a%0a%5b%2a%2a%2a%2aClosingBrace%28s%29Inserted%2a%2a%2a%2a%5d">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

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