Plotted entries from OPSLOG files in VIRCAM report ZP_Y_AVG, plot 2 (data set det_all):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS		det_ID     	values
====================================================
2014-12-23	57015.012919	DET1.CHIP1	23.51050377
2014-12-23	57015.012920	DET1.CHIP2	23.17976189
2014-12-23	57015.012921	DET1.CHIP3	23.27013779
2014-12-23	57015.012922	DET1.CHIP4	23.41031265
2014-12-23	57015.012923	DET1.CHIP5	23.44874382
2014-12-23	57015.012924	DET1.CHIP6	23.49896812
2014-12-23	57015.012925	DET1.CHIP7	23.4074688
2014-12-23	57015.012926	DET1.CHIP8	23.32729912
2014-12-23	57015.012927	DET1.CHIP9	23.41335678
2014-12-23	57015.012928	DET1.CHIP10	23.39814949
2014-12-23	57015.012929	DET1.CHIP11	23.37479019
2014-12-23	57015.012930	DET1.CHIP12	23.5114994
2014-12-23	57015.012931	DET1.CHIP13	23.21235085
2014-12-23	57015.012932	DET1.CHIP14	23.39467049
2014-12-23	57015.012933	DET1.CHIP15	23.42097664
2014-12-23	57015.012934	DET1.CHIP16	23.13153076