Plotted entries from OPSLOG files in ISAAC report OPTDIST_SLZ, plot 6 (data set p_F_A):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2012-04-29	56047.542509	-1.01536134190417e-05