[Aavso-photometry] FITS Keyword List

[Michael Newberry]

Brian,

Relatively few of the keywords listed have been invented by us for Mira 
purposes. For example, GAIN and RDNOISE are pretty well universally adopted. 
The core FITS standard is actually quite small and it has been the 
"conventional" keywords that really have come to be the carrier of a lot of 
FITS information. As I have mentioned before, it has long been critically 
important that images be able to go between Mira and IRAF and vice versa as 
easily as possible, so the keyword set used by Mira largely just reflects 
the keyword set that evolved in IRAF (and which also are supported by 
STSDAS, SAOImage, and other software). So it has been like "OK, tell us what 
you use and that's what we'll use" whenever possible, although with FITS 
there always are openings for new private keywords that may be needed. Thus 
there are a few photometry keywords we invented to hold the photometric zero 
point calculation. In addition, many of the the camera-related  keywords got 
entrenched at professional observatories worldwide in the early/mid 1980's 
by Photometrics, Ltd., who was the first major enterprise to produce cooled 
scientific CCD cameras along with control software. Well, that's about all I 
can say as to why the keywords listed are those that are listed.

Michael

----- Original Message ----- 
From: "Brian D. Warner" <brian at minorplanetobserver.com>
To: <aavso-photometry at mira.aavso.org>
Sent: Friday, January 04, 2008 12:56 PM
Subject: [Aavso-photometry] FITS Keyword List


> Michael,
>
> Thanks for that, but that only verifies what Mira uses. You say it is what
> professionals use but, as I've said publicly and privately, I've found 
> several
> professional sites that offer their own set of keywords, i.e., there is no
> direct evidence of "one FITS standard" beyond a limited set (see 
> immediately
> below).
>
> I went to
>
>  http://fits.gsfc.nasa.gov/fits_home.html
>
> and searched through what documentation I could find
>
> and specifically to
>
>  http://heasarc.gsfc.nasa.gov/docs/fcg/standard_dict.html
>  http://heasarc.gsfc.nasa.gov/docs/fcg/common_dict.html
>
>
> There is no mention of GAIN or RDNOISE (?) as adopted FITS standard or 
> even
> commonly used keywords, those being two words you specifically mentioned
> as being part of the standard. The second link provides links to other
> keyword dictionaries - extensions on the core standard, but I could not
> find those words.
>
> They may be on your list but they are not in the documentation, at least 
> that
> I could find. By providing this list, you've effectively said that we 
> should
> accept the Mira list as "official" somehow (please note the quotes) since 
> Mira
> is in compliance with the one standard.
>
> If that one standard truly does not include some of the keywords used by 
> Mira,
> i.e., I didn't overlook them, then it really comes down to your list being 
> yet
> another extension of the standard keywords. That's fine but why does that 
> make
> it specifically in compliance with the one standard?
>
> This discussion was premised on how software should comply with that one
> standard and went on to say that certain words are used or not used as 
> they
> should be. However, without having access to _independent_ documentation 
> of
> the standard, how can any of us decide if the software we use or write is
> in compliance? All we have at this point is information to make other 
> software
> compatible with Mira but no independent confirmation of the "one FITS 
> standard."
>
> I'll ask again, if these are not the correct URLs for documentation on the 
> one
> standard, then what are?
>
>
> 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
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