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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. <US Naval Observatory (1997)>
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 File Summary:
FileName Lrecl Records Explanations
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/* 0 6 Postscript documentation
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.
See also: : 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
Bytes Format Units Label Explanations
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 I1 --- Vflag *[1]? Verification Flag
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.
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
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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