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	0.122	22 27 45.74352	+09 05 20.7600	0975-20950407	336.940598	+09.089100			17.3	16.8	1954.578

%0a%0a%3cP%3e%0a%3cFONT%20SIZE=%27-1%27%3e%3cEM%3e%3cFONT%20COLOR=%27#0000FF%27>%3cB%3eNote:%20%3cB%3e%3cFONT%20COLOR=%27#CD5B45%27>%20The%20current%20version%20includes%20only%20the%20North%20%28POSS-I%20plates%29%3cP%3e%0a

Full	_r arcsec	_RAJ2000 "h:m:s"	_DEJ2000 "d:m:s"	APM-ID	RAJ2000 deg	DEJ2000 deg	rmag mag	l_	rClass	rStel	rDiam arcsec	rEll	bmag mag	l_	bClass	bStel	bDiam arcsec	b-r mag	Mflag
1	0.357	22 27 45.75936	+09 05 20.8104	EO1157-0024981	336.940664	+09.089114	16.77		1	3.41	9.7	0.03	17.63		-1	0.63	9.7	0.86
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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.

Full	_r arcsec	_RAJ2000 "h:m:s"	_DEJ2000 "d:m:s"	GSC2.2	RA(ICRS) deg	DE(ICRS) deg	Epoch yr	Rmag mag	e_ mag	Bjmag mag	e_ mag	Class	a pix	e
1	0.008	22 27 45.73680	+09 05 20.6880	N00312321470	336.940570	+09.089080	1987.716	16.55	0.38	17.58	0.40	3	3.97	0.11

%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%2fgalaxy%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:%2f%2fwww.nofs.navy.mil%2fdata%2ffchpix%2f%20%3cBR%3e%0a%3cB%3e%3cFONT%20COLOR=%27#EE0000%27>%20Note%20that%20the%20star%2fgalaxy%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	0.031	22 27 45.73536	+09 05 20.7204	0990-0605472	336.940564	+09.089089	78	79	1975.8	0	0	5	17.64	16.85	17.86	15.41	15.09

%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%2f239%29,%20Tycho-2%20%28I%2f259%29,%20UCAC2%20%28I%2f289%29,%20and%20USNO-B1.0%0a%28I%2f284%29%20catalogs%20for%20astrometry%20and%20optical%20photometry,%20supplemented%0aby%202MASS%20%28II%2f246%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%2fLinux%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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