Plotted entries from OPSLOG files in VIMOS report MASK_ZERO, plot 4, data set parY0Q1:

DATE       MJD-OBS      parameter values
==========================================================================
2008-11-20 54790.928079 1071.77440904086	parY0Q1
2008-11-21 54791.873236 1070.83365321159	parY0Q1
2008-11-21 54791.890067 1071.72115654277	parY0Q1