ACDS V10.0 - Detailed Description of I/305

ACDS V10.0 - Sun Jan 19 07:59:37 CET 2025

| # Detailed Description of I/305 : The Guide Star Catalog, Version 2.3.2 (GSC2.3) (STScI, 2006) |

Note : this is the description file of the original catalog. This HTML page corresponds well to the original description, but some minor changes in the format may have been introduced in the FITS output files in order to allow for arithmetic operations on quantities such as coordinates and times. h:m:s and d:m:s units are normally converted into degrees, and YYYY-MM-DD into julian days.
Similarly, some slight changes may have been introduced in the units; the value given in the HTML files supersedes the value indicated in the ReadMe file for this catalogue.

    I/305         The Guide Star Catalog, Version 2.3.2   (GSC2.3)  (STScI, 2006)
    ================================================================================
    The Guide Star Catalogue, Version 2.3.2
        Lasker B., Lattanzi M.G., McLean B.J., et al.
       <Astron. J. 136, 735 (2008)>
       =2008AJ....136..735L
    ================================================================================
    ADC_Keywords: Surveys ; Positional data ; Magnitudes, photographic ; Morphology

    Description:
        The GSC II is an all-sky catalog based on 1" resolution scans of the
        photographic Sky Survey plates, at two epochs and three bandpasses,
        from the Palomar and UK Schmidt telescopes (DSS). Positions,
        magnitudes, and classifications are produced for all objects on each
        plate. The objects are then loaded into the COMPASS database, where
        multiple observations of the same object are matched and assigned a
        unique name.

        The GSC2.3 has no magnitude limit. The parameters of the bright
        objects, overexposed on the Schmidt plates, are taken from the Tycho-2
        (I/259) catalog. The computed proper motions are not yet publically
        available because of 10mas/year systematic errors discovered for the
        southern hemisphere that are still under investigation.

    Copyright:
        The GSC-II is copyrighted (c) 2001-2005 by the Association of
        Universities for Research in Astronomy, Inc.; see the copyright
        notices from:
          http://gsss.stsci.edu/Acknowledgements/DataCopyrights.htm

        Scientists and educators who are using these data for research,
        teaching purposes and other non-profit activities may freely use these
        data and we only request that you acknowledge the source in any
        publication (see the "Acknowledgements" section below).

        Commercial use of these data is prohibited without permission.
        Please contact STScI for further information regarding the different
        copyright holders from
          http://gsss.stsci.edu/Acknowledgements/DataCopyrights.htm

    Release Notes and Limitation Notice: see
        http://gsss.stsci.edu/catalogs/gsc/gsc2/gsc23/gsc23_release_notes.htm

    See also:
        http://gsss.stsci.edu/catalogs/gsc/gsc2/gsc2.htm : the GSC-II Home Page
        I/254 : The HST Guide Star Catalog, Version 1.2 (Lasker+ 1996)
        I/259 : The Tycho-2 Catalogue (Hog+ 2000)
        I/271 : The Guide Star Catalog, Version 2.2 (GSC2.2) (STScI, 2001)

    File Summary:

           FileName      Lrecl  Records   Explanations

    ×                   80        .   This file
    × ReadMe            80        .   This file
    × out.sam          205      100   Sample records of GSC2.3.2 (near 0+0)

    Byte-by-byte Description of file:  out.sam

       Bytes Format Units    Label   Explanations

       1- 10  A10   ---      GSC2.3  [NS0-9A-Z] Identification of the object (1)
      13- 22  A10   ---      GSC1    Identification in GSC Version 1 (Cat. I/254)
      25- 32  A8    ---      HTM6    [NS0-3] HTM-6 designation as in GSC2.2 (1)
      34- 43  F10.6 deg      RAdeg   Right Ascension (J2000), at "Epoch"
      44- 53  F10.6 deg      DEdeg   Declination in (J2000), at "Epoch"
      55- 59  F5.2  arcsec  e_RAdeg  Mean error on RAdeg (2)
      61- 65  F5.2  arcsec  e_DEdeg  Mean error on DEdeg (2)
      67- 74  F8.3  yr       Epoch   Epoch of the position
      77- 81  F5.2  mag      Fmag    ? Magnitude in F photographic band (red)
      84- 87  F4.2  mag      e_Fmag  ? Mean error on Fmag
      89- 90  I2    ---      n_Fmag  ? Coded emulsion / bandpass / filter (2)
      93- 97  F5.2  mag      jmag    ? Magnitude in Bj photographic band (blue)
     100-103  F4.2  mag      e_jmag  ? Mean error on jmag
     105-106  I2    ---      n_jmag  ? Coded emulsion / bandpass / filter (2)
     109-113  F5.2  mag      Vmag    ? Magnitude in V photographic band (green)
     116-119  F4.2  mag      e_Vmag  ? Mean error on Vmag
     121-122  I2    ---      n_Vmag  ? Coded emulsion / bandpass / filter (2)
     125-129  F5.2  mag      Nmag    ? Magnitude in N photographic band (0.8µm)
     132-135  F4.2  mag      e_Nmag  ? Mean error on Nmag
     137-138  I2    ---      n_Nmag  ? Coded emulsion / bandpass / filter (2)
     141-145  F5.2  mag      Umag    ? Magnitude in U band (Johnson)
     148-151  F4.2  mag      e_Umag  ? Mean error on Umag
     153-154  I2    ---      n_Umag  ? Coded emulsion / bandpass / filter (2)
     157-161  F5.2  mag      Bmag    ? Magnitude in B band (Johnson blue)
     164-167  F4.2  mag      e_Bmag  ? Mean error on Bmag
     169-170  I2    ---      n_Bmag  ? Coded emulsion / bandpass / filter (2)
         174  I1    ---      Class   [0,5] Object class (3)
     176-185  I10   ---      Status  Source status flag (4)
         186  A1    ---      M       [M] 'M' for multiple object (5)
     189-194  F6.2  pix      a       ? Semi-major axis of fitting ellipse
     196-199  F4.2  ---      e       ? Eccentricity of fitting ellipse
     201-205  F5.1  deg      aPA     ? Position angle (N->E) of fitting ellipse

    Note (1): The GSC2.3 identification differs from GSC2.2.
        Is is made of 10 characters, the first four representing the level-6
        HTM (Hierarchical Triangular Mesh) coded in base 36 (0..9 and A..Z),
        and the last 6 represent a zero-filled sequence number assigned to
        each source upon initial detection.

        The Hierarchical Triangular Mesh (HTM) is a recursive spatial indexing
        scheme dividing the unit sphere into spherical triangles, the number
        of triangles at level n being 8x4n (see details about HTM at
        http://www.sdss.jhu.edu/htm/). The level-6 HTM varies from N000 to
        NCN3 and S000 to SCN3, i.e. 16384*2 different regions.

        The designation of the corresponding GSC2.2 object, if existing,
        is made by replacing the 4 first digits of the GSC2.3 identifier
        by the 8 HTM6 digits, and removing the leading zeroes of the number
        made by digits 5-10 of the GSC2.3 identifier.
    Note (2): coded emulsion / bandpass / filter:
       ----------------------------------------------------------------------
       bcode  Name   Emulsion/Filter
       ----------------------------------------------------------------------
         0     Jpg   IIIaJ+GG395 (SERC-J/EJ)
         1      V    IIaD+W12    (Pal Quick-V)
         2      -    HST FGS
         3      B    (Johnson)
         4      V    (Johnson)
         5     Fpg   IIIaF+RG630  (ESO-R)
         6    V495   IIaD+GG495   (Pal QV/AAO XV)
         7      O    103aO+no filter (POSS-I Blue)
         8      E    103aE+red plexi (POSS-I Red)
         9     Fpg   IIIaF+RG630
        10      -    IIaD+GG495+yellow objective (GPO Astrograph)
        11      -    103aO+blue objective (Black Birch Astrograph)
        12      -    103aO+blue objective Black Birch Astrograph, GSC cal.)
        13      -    103aG+GG495+yellow objective (Black Birch Astrograph)
        14      -    103aG+GG495+yellow objective (Black Birch Astrograph, GSC)
        16     Vpg   IIIaJ+GG49
        18     Jpg   IIIaJ+GG385   (POSS-II Blue)
        19      U    (Johnson)
        20      R    (Johnson)
        21      I    (Johnson)
        22      U    (Cape)
        23      R    (Kron)
        24      I    (Kron)
        35     Fpg   IIIaF+RG610   (POSS-II Red)
        36     Fpg   IIIaF+OG590   (SERC-ER/SR, AAO-R/GR)
        37     Npg   IVN+RG9       (POSS-II IR)
        38     Npg   IVN+RG715     (SERC-IR)
        39     Jpg   IIaO+GG385    (ESO-B)
        41      BT   TYCHO-B
        42      VT   TYCHO-V
        43      -    IRAS 12micron
        44      -    IRAS 25 micron
        45      -    IRAS 60 micron
        46      -    IRAS 100 micron
        47      J    (2MASS)
        48      H    (2MASS)
        49      K    (2MASS)
        50      u'   (SDSS)
        51      g'   (SDSS)
        52      r'   (SDSS)
        53      i'   (SDSS)
        54      z'   (SDSS)
       ----------------------------------------------------------------------
    Note (3): the object class is defined as:
          0=star          1=Galaxy,          2=Blend
          3=Non-star      4=unclassified     5=Defect
        In the version 2.3.2, only values 0 and 3 are present.
    Note (4): the status code is a 10-digit field encoding the properties
         of the catalog object. This flag is 99999900 for a Tycho object.
      ----------------------------------------------------------------------
      ........xx Number of plates on which the object appeared.
      .......x.. Centroid type associated with the exported position, as:
                      0 = barycenter                  4 = multicircular
                      1 = circular gaussian           5 = multielliptical
                      2 = elliptical gaussian         6 = FPA + circular
                      3 = FPA-applied barycenter      7 = FPA + elliptical
                      (FPA = Fractional Pixel Allocation)
      ......x... Quality of exported J magnitude, as:
                      0 = not present     1 = fit     2 = extrapolated
      .....x.... Quality of exported F magnitude, as:
                      0 = not present     1 = fit     2 = extrapolated
      ....x..... Quality of exported V magnitude, as:
                      0 = not present     1 = fit     2 = extrapolated
      ...x...... Classification unanimity
                      0 = mixed vote                  2 = unanimous defect
                      1 = unanimous vote
      ..x....... Classification voters
                      0 = several 15um scan           2 = several 25um scan
                      1 = one 15um scan               3 = one 25um scan
      .x........ Processing status
                      0 = complete processing on all plates
                      1 = object too big (>2562 pix) on at least one plate
      x......... Deblending
                      0 = single object on all plates
                      1 = child (deblended) object on at least one plate.
      ----------------------------------------------------------------------
    Note (5): this flag concerns only the Tycho stars (Status=99999900)

    Acknowledgements:
        The Guide Star Catalogue-II is a joint project of the Space Telescope
        Science Institute and the Osservatorio Astronomico di Torino. Space
        Telescope Science Institute is operated by the Association of
        Universities for Research in Astronomy, for the National Aeronautics
        and Space Administration under contract NAS5-26555. The participation
        of the Osservatorio Astronomico di Torino is supported by the Italian
        Council for Research in Astronomy. Additional support is provided by
        European Southern Observatory, Space Telescope European Coordinating
        Facility, the International GEMINI project and the European Space
        Agency Astrophysics Division.
    ================================================================================
    (End)                                   Francois Ochsenbein [CDS]    19-Apr-2007