The Guide Star Catalog II (GSC-II) is an all-sky optical 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. This all-sky catalog will ultimately contains positions, proper motions, classifications, and magnitudes in multiple bandpasses for almost a billion objects down to approximately Jpg=21, Fpg=20. The GSC-II is currently used for HST Bright Object Protection and HST pointing. Looking ahead, the GSC-II will form the basis of the Guide Star Catalog for JWST. This was constructed in collaboration with ground-based observatories for use with the GEMINI, VLT and GALILEO telescopes
Note - always use the most recent version of GSC 2 (currently 2.3.4) for HST target coordinates!
+ the additional passbands are primarily from the POSSI-E, the POSSI-O and Palomar Quick-V surveys so only cover the northern heimpshere
* the computed proper motions are not yet publically available because we discovered a 10mas/year systematic error for the southern hemisphere that we are still investigating.
The Second Generation Guide Star Catalog : Description and Properties