Plotted entries from OPSLOG files in NACO report DARK, plot 2 (data set dark05_HC):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2012-05-19	56067.521002	2.52666664123535
2012-05-20	56068.583552	2.46000003814697
2012-05-21	56069.458258	2.39333319664001
2012-05-22	56070.561046	2.43333339691162