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	18.262	20 36 45.34944	-13 11 47.6232	0750-20240598	309.188956	-13.196562			18.3	16.1	1953.775
2	24.163	20 36 42.58872	-13 11 59.3628	0750-20239903	309.177453	-13.199823			16.8	15.7	1953.775

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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	18.040	20 36 45.32976	-13 11 47.5404	S33132029839	309.188874	-13.196539	1985.482	16.57	0.44	18.56	0.42	3	3.20	0.10
2	24.352	20 36 42.57960	-13 11 59.7120	S33132029769	309.177415	-13.199920	1985.482	16.60	0.44	17.37	0.42	0	3.10	0.08

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>	\BegDIVclass='sort-down ' </A>
dec 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	0.841	20 36 44.22936	-13 11 56.3712	0768-0748422	309.184289	-13.198992	311	89	1967.6	0	0	2		19.18	20.84
2	18.023	20 36 45.31944	-13 11 47.2812	0768-0748432	309.188831	-13.196467	82	43	1973.8	-8	8	5	19.13	16.40	18.12	16.19	15.35
3	22.339	20 36 43.76952	-13 12 16.8732	0767-0715013	309.182373	-13.204687	69	203	1987.2	0	0	3			21.40	19.41	18.42
4	22.974	20 36 42.74136	-13 12 03.2832	0767-0715005	309.178089	-13.200912	151	249	1978.8	0	0	4	19.37		18.35	17.57	17.70
5	24.376	20 36 42.57672	-13 11 59.6112	0768-0748411	309.177403	-13.199892	59	103	1973.8	0	0	5	17.69	15.95	17.01	16.13	15.91

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

Full	_r arcsec	_RAJ2000 "h:m:s"	_DEJ2000 "d:m:s"	NOMAD1	YM	RAJ2000 deg	DEJ2000 deg	r	pmRA mas/yr	e_ (...)	pmDE mas/yr	e_ (...)	Bmag mag	r_	Vmag mag	r_	Rmag mag	r_	Jmag mag	Hmag mag	Kmag mag	R
1	0.840	20 36 44.229336	-13 11 56.37012	0768-0810034	..	309.1842889	-13.1989917	B	0.0	0.0	0.0	0.0	20.840	B			19.180	e
2	18.022	20 36 45.319344	-13 11 47.28012	0768-0810044	.M	309.1888306	-13.1964667	B	-8.0	2.0	8.0	1.0	18.120	B			16.190	B	14.496	13.896	13.635
3	22.336	20 36 43.769328	-13 12 16.86996	0767-0784172	..	309.1823722	-13.2046861	B	0.0	0.0	0.0	0.0	21.400	B			19.410	B
4	22.974	20 36 42.741336	-13 12 03.27996	0767-0784164	..	309.1780889	-13.2009111	B	0.0	0.0	0.0	0.0	18.350	B			17.570	B
5	24.377	20 36 42.576672	-13 11 59.61012	0768-0810022	YM	309.1774028	-13.1998917	B	0.0	0.0	0.0	0.0	16.790	Y	16.430	Y	16.130	B	15.454	14.994	14.852

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>	\BegDIVclass='sort-down ' </A>
dec Full	_r arcsec	_RAJ2000 "h:m:s"	_DEJ2000 "d:m:s"	CMC14	f_	RAICRS deg	DEICRS deg	r'mag mag	Nt	Jmag mag	Hmag mag	Ksmag mag
1	18.076	20 36 45.32976	-13 11 47.4612	203645.3-131147		309.188874	-13.196517	16.856	3	14.497	13.896	13.636
2	24.533	20 36 42.56568	-13 11 59.6004	203642.5-131159		309.177357	-13.199889	16.689	1	15.454	14.995

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Full	_r arcsec	_RAJ2000 "h:m:s"	_DEJ2000 "d:m:s"	GSC2.3	RAJ2000 deg	DEJ2000 deg	Epoch yr	Fmag mag	jmag mag	Vmag mag	Nmag mag	Class	a pix	e
1	0.903	20 36 44.19504	-13 11 56.3460	SC82034270	309.184146	-13.198985	1981.434		20.51			3	2.23	0.29
2	18.047	20 36 45.33000	-13 11 47.5332	SC82009839	309.188875	-13.196537	1985.482	16.57	18.56		15.53	3	3.20	0.10
3	22.551	20 36 43.77696	-13 12 17.1288	SC82009679	309.182404	-13.204758	1985.482	19.33	20.92		18.48	3	2.00	0.10
4	22.611	20 36 42.80736	-13 12 04.7124	SC82009770	309.178364	-13.201309	1985.482	18.89	19.77			3	2.23	0.06
5	24.351	20 36 42.57960	-13 11 59.7084	SC82009769	309.177415	-13.199919	1985.482	16.60	17.37		15.89	3	3.10	0.08

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