Plotted entries from OPSLOG files in FORS2 report BIAS_med_master, plot 1 (data set parC1hm):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2012-02-04	55962.409512	201
2012-02-04	55962.441482	201.33332824707
2012-02-04	55962.528718	201
2012-02-07	55965.350226	200