ACRS - Astrographic Catalog of Reference Stars
For a number of years there has been a great demand for a high-density
catalog of accurate stellar positions and proper motions that maintains
a consistent system of reference over the entire sky. The Smithsonian
Astrophysical Observatory Star Catalog (SAO; SAO Staff 1966) has
partially met those requirements, but its positions brought to current
epochs now contain errors on the order of 1 second of arc, plus the
proper motions in the SAO differ systematically with one another
depending on their source catalogs.
With the completion of the Second Cape Photographic Catalogue (CPC2; de
Vegt et al. 1989), a photographic survey comparable in density to the
AGK3 (Dieckvoss 1975) was finally available for the southern
hemisphere. These two catalogs were used as a base and matched against
the AGK2 (Schorr & Kohlschuetter 1951-58), Yale photographic zones
(Yale Trans., Vols. 11-32), First Cape Photographic Catalogue (CPC1;
Jackson & Stoy 1954, 55, 58; Stoy 1966), Sydney Southern Star Catalogue
(King & Lomb 1983), Sydney Zone Catalogue -48 to -54 degrees (Eichhorn
et al. 1983), 124 meridian circle catalogs, and catalogs of recent
epochs, such as the Carlsberg Meridian Catalogue, La Palma (CAMC), USNO
Zodiacal Zone Catalog (Douglass & Harrington 1990), and the Perth 83
Catalogue (Harwood ) to obtain as many input positions as
possible. All positions were then reduced to the system of the FK4
(Fricke & Kopff 1963) using a combination of the FK4, the FK4
Supplement as improved by H. Schwan of the Astronomisches
Rechen-Institut in Heidelberg, and the International Reference Stars
(IRS; Corbin 1991), then combined with the CPC2 and AGK3. The total
number of input positions from which the ACRS was formed is 1,643,783.
The original catalog is divided into two parts. Part 1 contains the
stars having better observational histories and, therefore, more
reliable positions and proper motions. This part constitutes 78 percent
of the catalog; the mean errors of the proper motions are +/-0.47
arcsec per century and +/-0.46 arcsec per century in right ascension
and declination, respectively. The stars in Part 2 have poor
observational histories and consist mostly of objects for which only
two catalog positions in one or both coordinates were available for
computing the proper motions. Where accuracy is the primary
consideration, only the stars in Part 1 should be used, while if the
highest possible density is desired, the two parts should be combined.
The ACRS was compiled at the U. S. Naval Observatory with the intention
that it be used for new reductions of the Astrographic Catalogue (AC)
plates. These plates are small in area (2 x 2 deg) and the IRS is not
dense enough. Whereas the ACRS was compiled using the same techniques
developed to produce the IRS, it became clear as the work progressed
that the ACRS would have applications far beyond its original purpose.
With accurate positions and proper motions rigorously reduced to both
the FK4 and FK5 (Fricke et al. 1988) systems, it does more than simply
replace the SAO. Rather, it provides the uniform system of reference
stars that has been needed for many years by those who require
densities greater than the IRS and with high accuracy over a wide range
of epochs. It is intended that, as additional observations become
available, stars will be migrated from Part 2 to Part 1, with the hope
that eventually the ACRS will be complete in one part. Additional
details concerning the compilation and properties of the ACRS can be
found in Corbin & Urban (1989) except that the star counts and errors
given here supersede the ones given in 1989.
Corbin, T.E., & Urban, S. E. 1991, Astrographic Catalogue Reference Stars
(Washington, U.S. Naval Observatory)
The HEASARC revised this database table in August, 2005, in order to add
Source designation. Depending on position of source, it could be the BD, the
CD or the CPD designations. Stars which are not in any of these catalogs have
all been disgnated NN (for no name). For stars like these, refer to the
parameter ACRS ID for the preferred designation (i.e., the ACRS name).
Magnitudes are photographic and come from the AGK3 in the north, and the CPC2
in the south.
The Right Ascension of the object in the selected equinox.
The Declination of the object in the selected equinox.
The Galactic Longitude of the object.
The Galactic Latitude of the object.
The Right Ascension of the object, in sexagesimal format, as given in the
original catalog, in J2000 coordinates.
The Declination of the object, in sexagesimal format, as given in the
original catalog, in J2000 coordinates.
The Right Ascension of the object, in sexagesimal format, as found in the
original data, in B1950 coordinates.
The Declination of the object, in sexagesimal format, as found in the
original data, in B1950 coordinates.
The catalog part can be either 1 or 2, as discussed in the overview.
Stars in Part 1 of the catalog have the most reliable positions and
The mean error in the Right Ascension of the position at the original epoch, in
seconds of time.
The mean error in the Declination of the position at the original
epoch, in arcseconds.
The centennial proper motion in Right Ascension, B1950 system, in
seconds of time per century.
The centennial proper motion in Declination, B1950 system, in seconds
of time per century.
The mean error in the proper motion in Right Ascension, in seconds of time
per century. These proper motion errors were derived from the dispersion of
the catalog positions used to determine the proper motion.
The mean error in the proper motion in Declination, in arcseconds per
century. These proper motion errors were derived from the dispersion of the
catalog positions used to determine the proper motion.
The original epoch of the Right Ascension and the Right Ascension proper
motion. The original epoch parameters refer to the mean epoch of the mean
position from the respective proper motion solution.
The original epoch of the Declination and the Declination proper motion. The
original epoch parameters refer to the mean epoch of the mean position from
the respective proper motion solution.
The number of Right Ascension positions used to determine the proper
motion and mean position of this coordinate.
The number of Declination positions used to determine the proper motion
and mean position of this coordinate.
The sum of the weights of the catalogs used to determine the Right Ascension.
The sum of the weights of the catalogs used to determine the Declination.
An identifier for each star based upon the recommended IAU nomenclature
(per PASP, 102, 1444, 1990). A `J` inside the name indicates that the
following coordinates found in the name are in the Julian reference
system and are for the year 2000.0, the standard equinox designated for
Julian system coordinates.
A sequential number beginning with 1 for part 1, and with 500001 for Part 2.
These numbers will not remain ordered as stars migrate.
Bonner Durchmusterung number.
Cordoba Durchmusterung number.
Cape Photographic Durchmusterung number.
Identifier from the AGK3 Catalog.
Identifier from the Second Cape Photographic Catalogue.
The centennial proper motion in the Right Ascension coordinate
(J2000.0), in seconds of time per century.
The centennial proper motion in the Declination coordinate (J2000.0),
in arcseconds per century.
The original epoch for the source minus J2000 for the Right Ascension
coordinate, in centuries. Thus, if the original epoch of the RA for a
source were 1945.000, this parameter would have a value of -0.550.
The original epoch for the source minus J2000 for the Declination
coordinate, in centuries. Thus, if the original epoch of the
Declination for a source were 1945.000, this parameter would have a
value of -0.550.
Questions regarding the ACRS database table can be addressed to the
HEASARC User Hotline.
If you have any problems, please consult the help
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