Data Description

Individual images

Each exposure is available as a multi-extension FITS file containing all 10 CCDs. The images are fully detrended. The astrometric calibration is expressed in the header using the CD matrix and PV distortion keywords. The photometric calibration is described using the PHOTZP keyword. PHOTZP is the zero-point, including exposure time and extinction corrections. The photometric calibration is slightly different for each CCD.

There is an associcated weight image for each image, which has the value 1 or 0, depending on whether the pixel is usable. The masked pixels (value=0) include bad columns, hot pixels, areas covered by the auto-guider and cosmic rays.

Stacked images

The images are simple FITS files (not multi-extension FITS files) measuring about 10000 pixels by 10000 pixels (0.5 degrees by 0.5 degrees) in the case of the tiles and varying size (depending on the dither pattern) in the case of grouped images. They have a sky level of 0 counts. They are scaled to have a photometric zero-point of 30.000 in AB magnitudes. That is to say, for each source:

AB_magnitude = -2.5 * log10(ADU) + 30.000

Each stack has an associated weight image. These are delivered with in a compressed format. To decompress them, use CFITSIO's imcopy. For example:

imcopy G002.003.844+33.133.G.weight.fits.fz G002.003.844+33.133.G.weight.fits

The values of a weight map pixel is proportional to the inverse of the variance of that pixel in the main image.

Raw images

The original raw images are not available from the CADC. Raw Suprime-Cam CCD frames can be retrieved from either STARS) (Subaru Telescope ARchive System) for observers or SMOKA (public science data archive by ADC, NAOJ) for general archive users.