[Aavso-photometry] FITS Keyword List

[Brian D. Warner]

Hi Michael,

OK, that's a start. Going to

  <http://iraf.noao.edu/iraf/web/projects/ccdmosaic/imagedef/fitsdic.html>

The first thing that jumps out is in the first paragraph:

  Most of the keywords defined here will not be used. 

Then, going down to the first keyword listed, DATE-OBS, one that is specifically
covered in the FITS standard document:

   DESCRIPTION:
    Default date for the observation.  This keyword is generally not used
    and is DATE-OBS keyword for the start of the exposure on the detector
    is used.

You have to go down the page to find a different definition of DATE-OBS,
found in a different file of some sort, that does indicate that it's used.

So, that page could be very confusing. 

Of course, one person adopting this convention doesn't solve the problem. As you
noted, there are many critical values that don't use the same keyword and/or
formatting. Any software that hopes to be "universal" in that it can read any
other software must hope that at least the critical, common values will all be
stored the same way. So far, I haven't found that to be true and have at least
five different ways to get the date/time from the FITS header, and even that's
not guaranteed to work. 

As some one said about standards, "Surely, you jest."

Clear Skies,
Brian D. Warner
Palmer Divide Observatory/Space Science Institute
http://www.MinorPlanetObserver.com

Collaborative Asteroid Lightcurve Link (CALL)
http://www.MinorPlanetObserver.com/astlc/default.htm