FITS standard

Forums Variable Stars Error in ASIIMG FITS header FITS standard

Nick James

The FITS “standard” is irritatingly vague about things like this and, particularly for astrometry, it is really important to know what DATE-OBS means. In most software these days it is the time that the exposure starts but sometimes it isn’t. In “good” software there is often a comment along the lines of:

DATE-OBS= ‘2021-07-26T22:03:10’ / Start of exposure

but often there isn’t and so it is always worth checking for whatever image acquisition and processing software you use.