Image processing, astrometry, photometry, etc.
- Posts: 36
- Joined: 01 Oct 2019, 01:10
Can you please confirm what is the timestamp when recording airmass in FITS headers?
I assume it is the beginning of the exposure?
- Posts: 444
- Joined: 03 Dec 2018, 21:43
Hello, the airmass is calculated at mid-exposure.
Instead, DATE-OBS is always the start of exposure in the FITS standard, and mid-exposure is a calculated field, as: DATE-OBS + EXPOSURE/2.