Airmass incorrect in VPhot and after using Transform Applier

Technology VPhot
1

After returning from enforced 2 month break I am bedevilled by problems. That will teach me.
Now I notice the calculated Airmass in VPhot is wrong. I think I raised this before and was reassured that it can be ignored.
However I notice it is wrong in uploaded reports.
My target X Per was at altitiude of 60 degrees and VPhot and TA are returning an airmass of 2.25

2

A possibility here is using local civil time (with/without daylight savings offsets) rather than UT. Try to imagine there are no dates/times in astronomy except UT.

\Brian

3

Thanks Brian,
I went back and checked the original files from AISair computer and the times from that look correct. Some of the later airmass outputs from VPhot are as much as 4, so something is badly out. Anyone wanting to use the obs will see them as tainted at such an (incorrect) airmass. To add, I’m not doing anythng different to a thousand times before so somethng is awry. As I can’t control it I guess my only rather unsatisfactory recourse is to delete the airmass readings as none would be preferable to false.

4

I have checked FITS files from the AISair controller and those from ASTAP calibration and times, location(LAT, LONG) are correct. I’m wondering if it’s related to the (missing file) error message I received from TA described in earlier post. I hope somebody can advise as I face manually correcting airmass for hundreds of observations.