GSPC -II Program GOAL: extend GSPC-I photometry to B = V ˜ 20 add R band to calibrate red second-epoch surveys HOW: take B,V,R CCD exposures centered at GSPC-I faintest star OR conveniently close to POSS-II centers (for POSS-II offset plates)

The Data Given the long time span of this survey project, data come from different telescopes as well as different CCD cameras Size of camera fields vary from ˜ 3.5 arc minutes to ˜20 arc minutes Pixel scale ranges from ˜ 0.35 arc seconds/pixel to ˜ 0.7 arc seconds/pixel When appropriate, both long and short exposures are acquired Pre-selected sets of standard stars from the Landolt catalog are observed each night Common fields are also regularly observed

Example of CCD frames taken at the 0.9m ESO Dutch Crowded poor medium

Telescope usage and number of GSPC-II sequences collected (as of October 2001 )

Target sequences are 1780 (1478 GSPC-I centers POSS-II new sequences) Current in-house catalog contains 1619 sequences, of which 776 in the north and 856 in the south data from one and a half runs performed in semester 01A still to be included in catalog two more runs of 7 nights each, one at the ING/JKT and one at the CTIO 0.9m, to be performed in November/December Relevant Numbers

1794 GSPCII targets observed still remain Sky Coverage

Magnitude limit of current catalog sequences

Number of stars/sequence in current catalog

GSPC-II Reduction Pipeline Photometry carried out with pipeline software (ARLO, Casalegno 1998) developed under IRAF Astrometry done within ARLO - fit to DSS positions Catalog of all frame data is a flat ASCII file including photometric, astrometric and other relevant information about the original exposures IRAF tables including additional statistical information are generated along with the frame catalogs Object naming performed in IRAF/IDL (naming convention: S001-AAAA, S002-AAAB, etc…)

Photometric Accuracy Only fits to Landolt stars with rms better than 0.05 are accepted Aperture photometry is carried out with fixed radius (2.3FWHM or < 4.5”) therefore not reliable in crowded fields PSF photometry more stable, but need to be checked for systematic errors in case of bad choice of template stars for analytical PSF Zero-point errors of transformation to standard system is also critical because it induces a photometric error of comparable magnitude

Released Sequences 622 GSPC-II fields ( Bucciarelli, Garcia, Casalegno et al. 2001, A&A 368, 335), 744 northern and 444 southern fields data are from KPNO, CTIO and ESO, for a total of 153 observing nights Aperture photometry only selection criteria based on agreement between Aperture and PSF photometry: Linear regression M(apt) - M(psf) = Z + k M(apt) sequences for which |k| < 0.01 and rms < 0.3 mag were retained

Zero-point errors Cumulative Distributions

GSPC-I/GSPC-II Comparison 597 V objects rms 0.07 mag, mean mag 380 B objects rms 0.06 mag, mean mag

Comparison of 10 common fields CTIO/KPNO

Comparison of 47 common fields CTIO/ESO

Summary 95% of GSPC-II data secured and practically all reduced Spin-off of observing activity 622 photometric sequences made available to community QA of new set of sequences for second release in progress Plan to put images, along with photometric reduction files, on-line for easy retrieval