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We are about to update the system clocks, so starting from next night, the timestamps in the FITS headers should be correct again! :-)

We've also monitored the time offset over the last couple of days, hoping that we might be able to correct timestamps in older data.

As you can see, the drift in time as compared to a time server is pretty large with almost a second per day. We tried to fit this drift with a linear and a quadratic function.

f(x)=a+bx:

degrees of freedom    (FIT_NDF)                        : 29
rms of residuals      (FIT_STDFIT) = sqrt(WSSR/ndf)    : 0.033795
variance of residuals (reduced chisquare) = WSSR/ndf   : 0.00114211

Final set of parameters            Asymptotic Standard Error
=======================            ==========================

a               = 50.289           +/- 0.01628      (0.03237%)
b               = 0.931105         +/- 0.005289     (0.5681%)

g(x)=c+dx+ex²:

degrees of freedom    (FIT_NDF)                        : 28
rms of residuals      (FIT_STDFIT) = sqrt(WSSR/ndf)    : 0.0113919
variance of residuals (reduced chisquare) = WSSR/ndf   : 0.000129776

Final set of parameters            Asymptotic Standard Error
=======================            ==========================

c               = 50.457           +/- 0.01242      (0.02462%)
d               = 0.788041         +/- 0.009657     (1.225%)
e               = 0.0253948        +/- 0.001685     (6.634%)

If you prefer to do your own fit, here is the list of data points (1st column JD of measurement, 2nd column offset in seconds):

2456755.99709491 51.28
2456755.99732639 51.28
2456756.01821759 51.30
2456756.05855324 51.32
2456756.59315972 51.77
2456756.62510417 51.80
2456756.75011574 51.91
2456756.87510417 52.01
2456757.00010417 52.11
2456757.12511574 52.22
2456757.25010417 52.34
2456757.37510417 52.47
2456757.50010417 52.59
2456757.62510417 52.71
2456757.75011574 52.83
2456757.87510417 52.94
2456758.00010417 53.05
2456758.12510417 53.17
2456758.25010417 53.29
2456758.37510417 53.41
2456758.50010417 53.54
2456758.62511574 53.66
2456758.75010417 53.78
2456758.87510417 53.90
2456759.00011574 54.02
2456759.12510417 54.14
2456759.25010417 54.26
2456759.37510417 54.39
2456759.50010417 54.51
2456759.62510417 54.64
2456759.75011574 54.76