# 3.6 gsc23_original_valid

GSC 2.3 Catalogue
Reference paper: Lasker et al. 2008, AJ 136,735
Original catalogue: R. Smart private communication

Columns description:

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.

fpg_mag : Rf photographic magnitude (double, Magnitude[mag])

Magnitude in Rf photographic band (red).

fpg_mag_error : Reference error on Rf (double, Magnitude[mag])

Reference error in Rf photographic band (red).
These photometric errors are not formal statistical uncertainties but raw and conservative estimates to be used for telescope operations.

fpg_mag_code : Rf filter Code (short)

coded emulsion / bandpass / filter:
———————————————————————-
bcode Name Emulsion/Filter
———————————————————————-
35 Fpg IIIaF+RG610 (POSS-II Red)
36 Fpg IIIaF+OG590 (SERC-ER/SR, AAO-R/GR)
———————————————————————-

jpg_mag : Bj photographic magnitude (double, Magnitude[mag])

Magnitude in Bj photographic band (blue).

jpg_mag_error : Reference error on Bj (double, Magnitude[mag])

Reference error in Bj photographic band (blue).
These photometric errors are not formal statistical uncertainties but raw and conservative estimates to be used for telescope operations.

jpg_mag_code : Bj filter Code (short)

coded emulsion / bandpass / filter:
———————————————————————-
bcode Name Emulsion/Filter
———————————————————————-
0 Jpg IIIaJ+GG395 (SERC-J/EJ)
18 Jpg IIIaJ+GG385 (POSS-II Blue)
———————————————————————-

v_mag : V (photographic) magnitude (double, Magnitude[mag])

Magnitude in V band.
This magnitude may include:

• photographic V${}_{1}2$ or V${}_{4}85$ from IIaD plates,

• V${}_{T}$ of Tycho-2 stars, or

• Johnson V from SKY2000

v_mag_error : Reference error on V (double, Magnitude[mag])

Reference error in V band.
These photometric errors are not formal statistical uncertainties but raw and conservative estimates to be used for telescope operations.

v_mag_code : V filter Code (short)

coded emulsion / bandpass / filter:
———————————————————————-
bcode Name Emulsion/Filter
———————————————————————-
4 V (Johnson)
6 V495 IIaD+GG495 (Pal QV/AAO XV)
42 VT TYCHO-V
———————————————————————-

npg_mag : In photographic magnitude (double, Magnitude[mag])

Magnitude in In photographic band.

npg_mag_error : Reference error on In (double, Magnitude[mag])

Reference error in In photographic band.
These photometric errors are not formal statistical uncertainties but raw and conservative estimates to be used for telescope operations.

npg_mag_code : In filter Code (short)

coded emulsion / bandpass / filter:
———————————————————————-
bcode Name Emulsion/Filter
———————————————————————-
37 Npg IVN+RG9 (POSS-II IR)
38 Npg IVN+RG715 (SERC-IR)
———————————————————————-

b_mag : B magnitude (double, Magnitude[mag])

Magnitude in B band.
This filter may include:

• B${}_{T}$ of Tycho-2 stars,

• Johnson B from SKY2000, or

• photographic O from pOSS-I.

b_mag_error : Reference error on B (double, Magnitude[mag])

Reference error in B band.
These photometric errors are not formal statistical uncertainties but raw and conservative estimates to be used for telescope operations.

b_mag_code : B filter Code (short)

coded emulsion / bandpass / filter:
———————————————————————-
bcode Name Emulsion/Filter
———————————————————————-
3 B (Johnson)
7 O 103aO+no filter (POSS-I Blue)
41 BT TYCHO-B
———————————————————————-

classification : Morphological classification (short)

Image classification:
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 SKY2000 object.

digit explanation values ……..xx Number of plates on which the object appeared …….x.. Centroid type associated with the exported position 0 = barycenter 1 = circular gaussian 2 = elliptical gaussian 3 = FPA-applied barycenter 4 = multicircular 5 = multielliptical 6 = FPA + circular 7 = FPA + elliptical ……x… Quality of exported J magnitude 0 = not present 1 = fit 2 = extrapolated …..x…. Quality of exported F magnitude 0 = not present 1 = fit 2 = extrapolated ….x….. Quality of exported V magnitude 0 = not present 1 = fit 2 = extrapolated …x…… Classification unanimity 0 = mixed vote 1 = unanimous vote 2 = unanimous defect ..x……. Classification voters 0 = several 15um scan 1 = one 15um scan 2 = several 25um 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.
FPA = Fractional Pixel Allocation)

mult_flag : Multiple object flag (short)

This flag concerns only the Tycho stars (Status=99999900).