Plotted entries from OPSLOG files in VIMOS report BIASNOISE, plot 8 (data set parQ4hi):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2012-05-20	56068.444640	3.15835087439423
2012-05-21	56069.440073	3.02006091026931
2012-05-22	56070.458650	3.1391026409863
2012-05-23	56071.400774	3.09715965841778