Trending is done only for the SR collimator. For the old CCD (until
2007-03-25) only 1x1 binning data are trended. For the new CCDs (since
2007-04-01) only 2x2 binning data are trended. Photometric nights are
selected from the Absorption Monitor. Zeropoints are per frame for flux in
e-/sec, not in ADU. Do <b> not use these zeropoints for science
data</b>. They are reduced assuming a standard extinction value, which
may not be correct for an individual night!