Imaging throughput is tabulated in the form of photometric zero points for griz bands for GMOS-N, and ugriz for GMOS-S.  The AB zero-point magnitudes are given by:

m_std = m_zero - 2.5 log (Ne/t) - k (μ -1),

where Ne is the background-subtracted number of electrons within the aperture, t is the exposure time, μ is the airmass, and CT is the color term coefficient.  The AB magnitudes were measured within an aperture that is equal to 4 times the FWHM of the images, so they are insensitive to seeing variations.  A detailed description of the data reduction procedures can be found in Jorgensen (2009).  For other details, including information on standard fields adopted on both sites, please, consult the GMOS photometric standards page.  Currently, zero points are only provided for CCD 2 and color terms are not being monitored.  Further calibrations will be performed for the remaining CCDs and will be made available soon.  For the data, follow the links below: