I/247 The AC2000 Catalogue (Urban+ 1997)
The AC2000: the Astrographic Catalogue on the Hipparcos System
Urban S.E., Corbin T.E., Wycoff G.L.
ADC_Keywords: Positional data ; Astrographic zones ; Surveys
Description:
The Astrographic Catalogue (AC) was an international effort designed
to photograph and measure the positions of all stars brighter than
magnitude 11.0. In total, some 4.6 million stars were observed, many
as faint as 13th magnitude. Users should realize that a few thousand
of the brightest stars are not included; their images on the source
plates were grossly over-exposed and therefore measurements were often
not made. This project was started over 100 years ago, and the
positions that have been derived from the AC data are being used, in
combination with modern epoch positions, to determine accurate proper
motions.
The United States Naval Observatory has completed the reductions of
the Astrographic Catalogue data (AC) to a consistent system. The
resulting catalog, called AC 2000, contains 4,621,836 stars covering
the entire sky, at an average epoch of 1907. The positions are on the
Hipparcos reference frame (J2000.0) at the epochs of observation.
Each of the 22 zones making up the Astrographic Catalogue was reduced
independently using the Astrographic Catalog Reference Stars (ACRS).
Each was analyzed for tilt, radial and tangential distortions, coma,
magnitude equation and non-symmetric field distortions. Following
these reductions, the data were placed on the Hipparcos system and the
magnitudes were converted to be close to that of the Tycho B data. The
resulting data were then combined into the final catalog. Detailed
information on the reduction methodology and input data can be found
in the file "intro.tex", or in the postscript documents provided
provided in the "ps" subdirectory.
The data contain the positions (eq. J2000.0) at mean epochs of
observation, magnitude estimates and accuracy estimates for each star.
Cross identifications with the Hipparcos Catalogue, Tycho Catalogue
and the Astrographic Catalog Reference Stars are provided to
facilitate future work with these stars. Interested parties are
encouraged to visit the AC web site at
http://aries.usno.navy.mil/ad/ac.html.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ac_p60.dat 93 258702 Stars with declinations +60 to +90 degrees (1)
ac_p50.dat 93 244786 Stars with declinations +50 to +59 59 59.99 (1)
ac_p40.dat 93 203384 Stars with declinations +40 to +49 59 59.99 (1)
ac_p30.dat 93 380791 Stars with declinations +30 to +39 59 59.99 (1)
ac_p20.dat 93 354034 Stars with declinations +20 to +29 59 59.99 (1)
ac_p10.dat 93 316299 Stars with declinations +10 to +19 59 59.99 (1)
ac_p00.dat 93 297613 Stars with declinations +00 to +09 59 59.99 (1)
ac_n00.dat 93 284057 Stars with declinations -00 to -09 59 59.99 (1)
ac_n10.dat 93 383616 Stars with declinations -10 to -19 59 59.99 (1)
ac_n20.dat 93 380220 Stars with declinations -20 to -29 59 59.99 (1)
ac_n30.dat 93 347380 Stars with declinations -30 to -39 59 59.99 (1)
ac_n40.dat 93 463848 Stars with declinations -40 to -49 59 59.99 (1)
ac_n50.dat 93 363810 Stars with declinations -50 to -59 59 59.99 (1)
ac_n60.dat 93 343296 Stars with declinations -60 to -90 degrees (1)
intro.tex 125 1830 Original Introduction (latex)
ps/* . 6 Postscript documentation
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Note (1): all these files should be concatenated to give the
full AC J2000 catalog, split here into 14 files.
Within each file, stars are ordered by increasing right ascension.
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See also:
http://aries.usno.navy.mil/ad/ac.html : AC web site
I/171 : Astrographic Catalog Reference Stars (ACRS) (Corbin+ 1991)
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
I/246 : The ACT Reference Catalog (Urban+ 1997)
Byte-by-byte Description of file: ac*.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right Ascension (ICRS) at Epoch (hours)
4- 5 I2 min RAm Right Ascension (ICRS) at Epoch (minutes)
7-12 F6.3 s RAs Right Ascension (ICRS) at Epoch (seconds)
14 A1 --- DE- Declination (ICRS) at Epoch (sign)
15-16 I2 deg DEd Declination (ICRS) at Epoch (degrees)
18-19 I2 arcmin DEm Declination (ICRS) at Epoch (minutes)
21-25 F5.2 arcsec DEs Declination (ICRS) at Epoch (seconds)
27-31 F5.2 mag Bmag Magnitude from image diameters
33-40 F8.3 yr Epoch Mean epoch of position
42-43 I2 --- Num Number of images used
44-49 F6.3 arcsec e_RAs ?Standard deviation of mean, RA
50-55 F6.3 arcsec e_DEs ?Standard deviation of mean, Dec
57-64 I8 --- AC2000 AC 2000 Number
66-71 I6 --- HIP ?Hipparcos Number (Cat. I/239)
73-84 A12 --- TYC *?Tycho ID (Cat. I/239)
86-92 I7 --- ACRS ?ACRS number (Cat. I/171)
93-93 I1 --- Vflag *[1]? Verification Flag
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Note on TYC:
Tycho "number" originally had embedded blanks. These embedded blanks
have been converted to zeros.
Note on Vflag:
The Verification flag is either blank or '1'. When set to '1', the
star has not been found in Hipparcos, Tycho, ACRS, the overlapping AC
plate or in the GSC 1.2. These records should be used with caution.
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Acknowledgements:
Reductions by the Astrometry Department
U.S. Naval Observatory
3450 Massachusetts Ave. NW
Washington, DC 20392-5420
e-mail:
Usage Notice:
Any use of the data in publication must be accompanied by a citation
as to the original author.
History:
The data are a copy of the CD-ROM "The AC 2000 Catalog" from
U.S. Naval Observatory, September 1997.
(End) Sean E. Urban [U.S. Naval Observatory] 10-Nov-1998