Photometric calibration
The data are calibrated to a common zeropoint of 24 mag for all bands, with an exposure time (exptime) of 53.907456 sec. The pixel size is 0.396 arcsec. AB magnitudes can be derived from the data via:
mag = -2.5 x log10(counts/exptime) + 24
μ(mag arcsec⁻²) = -2.5 x log10(counts/exptime) +5 x log10(pix) + 24
or
mag = -2.5 x log10(counts) + 28.3291
μ(mag arcsec⁻²) = -2.5 x log10(counts) + 26.3176
Each coadded image has an exposure time map attached to it. Each pixel value in the map is the number of single images n(x,y) contributing to the stack. The effective exposure time in each part of the image is then given by the product of n(x,y) and exptime.