Plotted entries from OPSLOG files in MIDI report REFPIX_OPEN, plot 4 (data set YAB2_OPEN_ops):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2012-05-21	56069.540336	165.997169
2012-05-22	56070.394711	165.9851
2012-05-23	56071.389039	165.949936