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  Query the Guide Star Catalog (GSC V2.3.2) at STScI by position


  Uses the IDL SOCKET command to query the GSC 2.3.2 database over the Web.
  Alternatively, (and more reliably) one can query the GSC 2.3.2 catalog using
  queryvizier.pro and the VIZIER database, e.g.
    IDL> st = queryvizier('GSC2.3',[23,35],10,/all)
  GSC2.3 is an all-sky export of calibrated photographic survey plate
  source parameters from the COMPASS database. The number of unique
  objects is approximately 945,592,683. All sources are
  from the second-generation plate-processing pipeline with the exception
  of Tycho-2 and Skymap sources in the case of very bright objects. The
  Skymap sources are exported when there is no matching GSC or Tycho
  sources. Each GSC 2.3 entry contains only one position and one
  magnitude per bandpass for each unique sky object

Calling Sequence

    info = QueryGSC(targetname_or_coords, [ dis, /HOURS] )


      TARGETNAME_OR_COORDS - Either a scalar string giving a target name,
          (with J2000 coordinates determined by SIMBAD), or a 2-element
          numeric vector giving the J2000 right ascension in *degrees* (or
          hours if /HOURS is set) and the target declination in degrees.

Optional Input

    dis - Numeric scalar giving search radius in arcminutes to search around
          specified target Default is 5 arcminutes

Optional Input Keywords

    /BOX - if set, then radius gives a box width in arcminutes
    /HOURS - If set, then the right ascension is both input and output (in
            the info .ra tag) in hours instead of degrees
    /VERBOSE - If set, then the CGI command to the Webserver will be displayed


  info - IDL structure containing information on the GSC stars within the
          specified distance of the specified center. There are (currently)
          23 tags in this structure -- for further information see
          .HSTID - GSC 2.3 name for HST operations
          .GSC1ID - GSC1 name
          .RA,.DEC - Position in degrees (double precision). RA is given in
                  hours if the /HOURS keyword is set.
          .RAERR, .DECERR - uncertainty (in arcseconds) in the RA and Dec
          .EPOCH - mean epoch of the observation
          .FPGMAG, .FPGERR - magnitude and error in photographic F
          .JPGMAG, .JPGERR - magnitude and error in photographic J
          .VPGMAG, .VPGERR - V magnitude and error
          .NPGMAG, .NPGERR - magnitude and error
          .UMAG, .UERR - magnitude and error
          .BMAG, .BERR - magnitude and error
          .VMAG, .VERR - magnitude and error
          .RMAG, .RERR - magnitude and error
          .IMAG, .IERR - magnitude and error
          .JMAG, .JERR - magnitude and error
          .HMAG, .HERR - magnitude and error
          .KMAG, .KERR - magnitude and error
          .A - semi-major axis in pixels
          .PA - Position angle of extended objects in degrees
          .E - eccentricity of extended objects
          .CLASS - classification (0-5): 0-star, 1-galaxy, 2-blend,
                        3-nonstar, 4-unclassified, 5-defect
          .STATUS -10 digit field used to encode more detailed information
              about the properties of the catalog object. For more info, see
          .VFLAG, MFLAG - Variability nad multiplicity flags
            .FPGBAND, .NPGBAND, .JPGBAND. UBAND, BBAND, .VBAND - flag as
            to wether given bandpass is available


          Plot a histogram of the photographic J magnitudes of all GSC 2.3.2
          stars within 10 arcminutes of the center of the globular cluster M13
          IDL> info = querygsc('M13',10)
          IDL> plothist,info.jpgmag,xran=[10,20]

Procedures Used


Modification History

        Written by W. Landsman SSAI August 2002
        Fixed parsing of RA and Dec W. Landsman September 2002
        Major rewrite to use new STScI Web server, remove magrange
          keyword W. Landsman Dec 2007
        Update server name, added /BOX,/ VERBOSE keywords W.L 19 Dec 2007
        Web server now also returns infrared data W.L. Feb 2010
        Fixed case where dec neg. and deg or min 0 Pat Fry Jul 2010

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