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I/252 The USNO-A2.0 Catalogue (Monet+ 1998)
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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.
<U.S. Naval Observatory Flagstaff Station (USNOFS) and
Universities Space Research Association (USRA) stationed at USNOFS.
(1998)>
=1998USNO2.C......0M
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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. <I/220>) as its reference frame whereas A2.0 uses the ICRF as
realized by the USNO ACT catalog (Urban et al. 1997, see Cat.
II/246>).
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:
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FileName Lrecl Records Explanations
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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/* . . *Directory for region files
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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.
Note on usnoa/*: The region files were copied from the Flagstaff FTP site.
Each of the 24 pieces of the catalog contains 2 files, and the
naming convention is
zoneXXXX.YYY
XXXX is 10 times the Solar Polar Distance (SPD) (0, 75, 150, ... 1725)
YYY = acc (ASCII accelerator file)
= cat (binary catalog file)
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See also:
ftp://ftp.nofs.navy.mil/usnoa : The Flagstaff FTP site with
the original catalogue
http://ftp.nofs.navy.mil/projects/pmm/ : The Precision Measuring Machine
home page at Flagstaff Station, U.S. Naval Observatory
Byte-by-byte Description of file: out.sam
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Bytes Format Units Label Explanations
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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. <I/246>)
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
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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), a dash (-)
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.
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History:
* 03/28/2001 The region files were copied from the Flagstaff FTP site. [ADC]
Acknowledgements:
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
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(End) Francois Ochsenbein [CDS] 27-Oct-1998