Picturing the Guide Star Catalog
Telescope Data Center
Smithsonian Astrophysical Observatory
The information contained in the two CDROMs of the Hubble Space Telescope
Guide Star Catalog has been condensed into a series of all-sky images.
images show V-filter flux for
Magnitudes of Guide
Stars in the southern hemisphere differ systematically from those in the
northern hemisphere due to the different plate emulsion and filter used.
Individual object fluxes cannot be calibrated accurately, but by using
a large number (16,000 for the first pass, 180,000 for the second) of
sources near the equator which were measured on both Palomar and SERC plates,
an average calibration can be fit. An intermediate step in the calibration
produced a catalog of 180,524 objects in the GSC for which measurements at
two colors exist. A catalog binning program, SKYPIC, developed from SKYMAP
was used to produce two-dimensional FITS images of Guide Star Catalog fluxes
with southern hemisphere plate magnitudes recalibrated to match the northern
hemisphere plate V magnitudes. Maps of non-stellar source density, as well
as flux, show excesses at the edges of plates, so care should be taken to
avoid plate edges when applying characteristics of the Guide Star Catalog to
the real universe.
Presented at the Third Annual Conference on Astronomical Data Analysis
Software and Systems
(ADASS 93) in Victoria, British Columbia October 1993.
in Astronomical Data Analysis Software and Systems III,
A.S.P. Conference Series, Vol. 61, 1994, Dennis R. Crabtree, R.J. Hanisch,
and Jeannette Barnes, eds., p. 191.