A data reduction pipe-line was made by Andreas Jaunsen who kindly has performed the photometric analysis. The photometric standard cluster positions and exposure times we use. They are all among the Stetson Photometric Standard Fields . Observations should be performed at 3 different airmasses in photometric conditions.
Online catalogue is zpmon.cat .
Sky flat fields and bias frames are needed, as well. Note that in some cases the extinction coefficients were not determined from the observations on that night, but fixed extinction values were used.