Publications

The Guide Star Photometric Catalog-II (GSPC-II) is being created by the STScI Catalogs and Survey Branch and the Osservatorio Astronomico di Torino (OATo) to provide photometric calibrators for the Guide Star Catalog-II (GSC-II). Most of the GSPC-II star sequences extend the GSPC-I sequences to a limiting magnitude of V = 19 or fainter based on CCD data in the V and R bandpasses of the Johnson-Kron-Cousins system. Where resources were available, which is for a large part of the southern hemisphere and for a few northern fields, a B band was also included, and the limiting magnitude brought to ~20. While the southern second-epoch plates used for GSC-II lie on the same 5 deg grid pattern used for for GSC-I and require no additional sequences, the northern POSS-II plates supporting GSC-II lie on a similar 5 deg grid which differs from the 6 deg grid used for GSC-I. This results in a number of POSS II plates being considerably shifted with respect to the original grid, and therefore poorly covered by the GSPC-I sequences. New northern sequences are being added in GSPC-II to support calibration of such POSS-II plates.

The observations were obtained with mostly one-meter class telescopes at ten observatories. Most of the northern GSPC-II sequences were imaged at the Kitt Peak and Wise Observatories, whereas southern declinations were covered by Cerro Tololo and ESO-La Silla observations. Data also were acquired at Mt. Hopkins, Mt. Laguna, Lowell, Mt. Megantic, McDonald and JKT La Palma observatories. The observation strategy was to take CCD frames centered on the faintest star of the corresponding GSPC-I sequence where one was available. When necessary, both long (~8-15 min) and short (<3 min) exposures were acquired in each field. Short exposures times were chosen to be appropriate for the typical 14.5 mag target star. For new POSS-II fields lacking GSPC-I sequences, the telescope was pointed to the nominal center of the corresponding survey plate, and the pointing adjusted to avoid bright stars.

For more information see: the journal article: "An All Sky Set of (B)- V-R Photometric Calibrators for Schmidt Surveys: GSPC2.1: First Release", Bucciarelli, et al. A&A 368, pp 335-346, 2001