Plotted entries from OPSLOG files in NACO report SLIT, plot 1 (data set ypos_HC):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2012-01-22	55949.408002	560.159901408167
2012-01-22	55949.408396	561.328502615224