Plotted entries from OPSLOG files in FORS2 report BIAS_med_master, plot 4 (data set parC2hm):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2013-05-14	56427.437166090000000	195.66667175293
2013-05-15	56428.448169190000000	195.66667175293
2013-05-16	56429.350134460000000	195
2013-05-17	56430.361892010000000	194.66667175293
2013-05-19	56432.464688940000000	195