GSC 2.3 Catalogue
Reference paper: Lasker et al. (2008)
Original catalogue: R. Smart private communication
gsc23_oid : Unique Numeric Identifier (long)
Incremental unique numeric identifier (increasing with declination).
This is the only field which was not in the original GSC2.3 catalogue, but was added for cross-match purposes.
gsc23_identifier : source Id in original catalog (string)
The GSC2.3 identification 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.
ra : RA, ICRS (double, Angle[deg])
J2000 right ascension with respect to the ICRS.
dec : DEC, ICRS (double, Angle[deg])
J2000 declination with respect to the ICRS.
position_epoch : Position Epoch (double, Time[Julian Years])
Plate epoch for GSC-II objects. For Tycho-2 objects, for which RA epoch and DEC epoch are different, the RA epoch is given.
ra_error : Reference error in RAcosDEC (double, Angle[arcsec])
Reference error in RA*cos(DEC) at position epoch (position_epoch). These astrometric errors are not formal statistical uncertainties but raw and conservative estimates to be used for telescope operations.
dec_error : Reference error in DEC (double, Angle[arcsec])
Reference error in DEC at position epoch (position_epoch). These astrometric errors are not formal statistical uncertainties but raw and conservative estimates to be used for telescope operations.
0 = ”star”, i.e. point-like object
3 = ”nonstar”, i.e. extended object
status : Object processing status flag (string)
The status code is a 10-digit field encoding the properties of the catalog object.
This flag is 99999900 for a Tycho object and 88888800 for a SKY2000 object.
digitexplanationvalues……..xxNumber of plates on which the object appeared…….x..Centroid type associated with the exported position0 = barycenter1 = circular gaussian2 = elliptical gaussian3 = FPA-applied barycenter4 = multicircular5 = multielliptical6 = FPA + circular7 = FPA + elliptical……x…Quality of exported J magnitude0 = not present1 = fit2 = extrapolated…..x….Quality of exported F magnitude0 = not present1 = fit2 = extrapolated….x…..Quality of exported V magnitude0 = not present1 = fit2 = extrapolated…x……Classification unanimity0 = mixed vote1 = unanimous vote2 = unanimous defect..x…….Classification voters0 = several 15um scan1 = one 15um scan2 = several 25um scan3 = one 25um scan.x……..Processing status0 = complete processing on all plates1 = object too big (2562 pix) on at least one platex………Deblending0 = single object on all plates1 = child (deblended) object on at least one plate. FPA = Fractional Pixel Allocation
mult_flag : Multiple object flag (short)
This flag concerns only the Tycho stars (Status=99999900).