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I/22A       Astrographic Catalogue (AC), -02/+04deg      (Lacroute+ 1981)
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Astrographic Catalogue: Alger zone
     Lacroute P., Valbousquet A.
    <Bull. Inform. CDS 6 (1974)>
    =1974BICDS...6...38L
     Valbousquet A.
    <Bull. Inform. CDS 13, 2 (1977)>
    =1977BICDS..13....2V
     Lacroute P.
    <Bull. Inform. CDS 21, 2 (1981)>
    =1981BICDS..21....2L
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ADC_Keywords: Positional data ; Astrographic zones ; Magnitudes, photographic

Description:
    The "Carte de Ciel" (or "Astrographic Catalogue") is a catalogue of
    star positions and magnitudes, determined on the photographic plates
    taken by the normal astrographs which are installed in observatories
    of various latitudes, as a world-wide astronomical project (see
    Eichhorn, 1974, p279). The catalogue is divided into 22 declination
    zones, each of which is assigned to each observatory, e.g., a zone
    from +18 to +24 degrees is to Paris observatory.

    Each observatory has taken photographs of 2 deg x 2 deg area in and
    covering each zone, measured the X,Y coordinates of star images on the
    photographic plates, and published the results as the printed
    catalogues. The present catalogue is the results of reduction of these
    X,Y coordinates into right ascension and declination values, for
    declination zones of +05 to +31, by using AGK2/3 catalogue as the
    reference.

Data completeness:
    Incompletenesses of the data are as follows:
    (1) The latter half of the data of zone +04 is missing.
    (2) Declination values for negative declination zones have
        different expres sions details of which are unknown.
    (3) X,Y coordinate values are attached but are different from
        those values published by Alger observatory.

File Summary:
--------------------------------------------------------------------------------
 FileName    Lrecl    Records    Explanations
--------------------------------------------------------------------------------
ReadMe          80          .    This file
catalog.dat     63     306432    Alger zone -02/+04 degrees
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See also:
  I/21  : Zones +05 to +31 (Alger zones) (Lacroute and Valbousquet, 1974)
  I/154 : Zones -02 to +31 degrees of AC (Roeser, 1990) (RA and DE files)
  I/155 : Zones -02 to +31 degrees of AC (Roeser, 1990) (X and Y files)
  I/171 : Astrographic Catalog Reference Stars (ACRS) (Corbin+ 1991)

Byte-by-byte Description of file: catalog.dat
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   Bytes Format  Units   Label    Explanations
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   1-  3  I3      deg      ZONE    *[-2/4] plate identifier
   4-  7  I4      ---      PLATE   *[-180/180] plate identifier
   8- 11  I4      ---      STAR     running number of star on the plate
  12- 21  I10     mas      RAmas    [0/1296000000[ right ascension  (B1950)
  22- 31  I10     mas      DEmas    [-324000000/324000000] declination  (B1950)
  32- 36  I5      0.01yr   EPOCH    [0/20000] plate epoch from 180000
  37- 39  I3      dmag     mB       [-99/999] photographic magnitude
  40- 47  I8      0.1um    X        [-9999999/9999999] X coordinate on the plate
  48- 55  I8      0.1um    Y        [-9999999/9999999] Y coordinate on the plate
  56- 58  I3      deg      AGK3Z   *[0/89]? AGK3 number : zone number
  59- 62  I4      ---      AGK3N    [1/9999]? AGK3 number : star number
      63  I1      ---      ZERO     [0] zero
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Note on ZONE:
        declination zone, or the declination of the center of each
        astrographic plate
Note on PLATE:
        running number of plate in the zone
        Note that this number is negative when the zone is negative.
Note on AGK3Z:
        No signs on any AGK3 zones.
--------------------------------------------------------------------------------

Historical Notes:
  * Originally the Paris zone was archived as I/22, and the Alger zone was
    included in I/21. However, the data format of Alger zone is different
    from others and the data have some incompleteness, and we rearranged
    them, separating the Alger zone data as I/22A.

References:
   Eichhorn H. (1974): Astrometry of Star Positions, Frederick Unger Publ.
      Co., New York.
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(End) Koichi Nakajima [CDS]   24-Sep-1993    J.A. Watko [SSDOO/ADC]  18-Jan-1996