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I/252 The USNO-A2.0 Catalogue (Monet+ 1998) ================================================================================ USNO-A V2.0, A Catalog of Astrometric Standards Monet D. Bird A., Canzian B., Dahn C., Guetter H., Harris H., Henden A., Levine S., Luginbuhl C., Monet A.K.B., Rhodes A., Riepe B., Sell S., Stone R., Vrba F., Walker R.================================================================================ ADC_Keywords: Surveys ; Positional data Description: USNO-A2.0 is a catalog of 526,280,881 stars, and is based on a re-reduction of the Precision Measuring Machine (PMM) scans that were the basis for the USNO-A1.0 catalog. The major difference between A2.0 and A1.0 is that A1.0 used the Guide Star Catalog (Lasker et al. 1986, see Cat. ) as its reference frame whereas A2.0 uses the ICRF as realized by the USNO ACT catalog (Urban et al. 1997, see Cat. ). A2.0 presents right ascension and declination (J2000, epoch of the mean of the blue and red plate) and the blue and red magnitude for each star. Usage of the ACT catalog as well as usage of new astrometric and photometric reduction algorithms should provide improved astrometry (mostly in the reduction of systematic errors) and improved photometry (because the brightest stars on each plate had B and V magnitudes measured by the Tycho experiment on the Hipparcos satellite). The basic format of the catalog and its compilation is the same as for A1.0, and most users should be able to migrate to this newer version with minimal effort. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file out.sam 55 100 *Sample output (out of 526,280,881 stars) read.me 79 353 Author's Original Catalogue Description usnoa/* . . Compact version of Catalogue (3.6Gbytes) -------------------------------------------------------------------------------- Note on out.sam: this file is actually the result of the execution of the query on the compacted version of USNO-A2.0 at CDS (in subdirectory usnoa, not yet accessible) -------------------------------------------------------------------------------- See also: ftp://ftp.nofs.navy.mil/usnoa : The Flagstaff FTP site with the original catalogue http://www.usno.navy.mil/pmm/ : The Precision Measuring Machine home page at Flagstaff Station, U.S. Naval Observatory Byte-by-byte Description of file: out.sam -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 13 A13 --- USNO-A2.0 *Original designation in USNO-A2.0 catalogue 15- 24 F10.6 deg RAdeg Right ascension (ICRS) mean of blue/red plates 25- 34 F10.6 deg DEdeg Declination (ICRS) mean of blue/red plates 35 A1 --- ACTflag [A] 'A' when star belongs to ACT (Cat. ) 36 A1 --- Mflag [*] '*' magnitudes are probably wrong 38- 41 F4.1 mag Bmag Magnitude from blue plate 43- 46 F4.1 mag Rmag Magnitude from red plate 48- 55 F8.3 yr Epoch *?=0.0 Mean epoch of position -------------------------------------------------------------------------------- Note on USNO-A2.0: This number allows to retrieve the exact original record: it is made of a zone number (4 digits from 0000 to 1725 representing the distance in 0.1deg to the South Pole, stepped by 75 = 7.5degrees), and a number in the area (8 digits, order by IRCS (J2000) RA); ****Note that this number differs from the USNO-A1.0 one. Note on Epoch: Epoch is the averaged date of observation between the blue and the red plates. -------------------------------------------------------------------------------- Author's Address: Dave Monet US Naval Observatory Flagstaff Station PO Box 1149 (US Mail Only) West Highway 66 (FedEx, UPS, etc.) Flagstaff AZ 86001 USA Voice: 520-779-5132 FAX: 520-774-3626 e-mail: dgm@nofs.navy.mil ================================================================================ (End) Francois Ochsenbein [CDS] 27-Oct-1998