Plotted entries from OPSLOG files in MIDI report REFPIX_HS, plot 8 (data set YB2_HS_ops):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2012-05-21	56069.540336	165.773005
2012-05-22	56070.394711	165.745348
2012-05-23	56071.389039	165.743104