Time Stamps

[Patrick]

Hello,
I refer to Astroart 9.0 SP4 User's Manual page 250, Section11.2, DATE-OBS '…the mid of exposure, which is used for all measures…".
Of all the possible image header keywords added by AA can you please clarify which are calculated/recorded as for mid-exposure?
I use IRAF and the data is sensutive to the time stamp of various values.

I read that the recorded airmass (also ST?) and alt/az coordinates are calculated at mid-exposure and I understand that DATE-OBS is reorded at the start of an exposure.
Regards,
Patrick.

[fabdev]

Hello,
DATE-OBS: start of exposure, as defined by the FITS standard.
ALT-AZ: mid of exposure.
AIRMASS: mid of exposure.
Sideral Time: start of exposure.

Clear skies,
Fabio.

[Patrick]

Thank you.
Patrick