[fitsbits] Proposed Changes to the FITS Standard

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On Tue, 21 Aug 2007, Maren Purves wrote:

> Hate to say this, but we're starting to have a generation
> problem. I got into FITS at the time of binary arrays,
> not at the start (so I'm in the 'middle; generation). 

Hmm ... if nearly contemporary to FITS (I graduated 1 month before 
FITS's birthday :-)) but of course wasn't in the Deciding Bodies that 
early (or as early as generalized extensions were introduced).

> do we still have FITS files without extensions?

I guess there will be plenty, those which the programmer-type people 
will ask "how different with JPEG".  Seriously, there is no need to use 
an extension for a plain image or even a datacube.

> It being "once FITS always FITS" I object to making the
> EXTEND keyword optional.

The "fault" about EXTEND was in its original definition. The keyword 
EXTEND=T was present "if the FITS file MAY contain extensions" and 
it being equal to T did "not imply extensions be present". As such it 
resembles a bit the present versioning/no-versioning discussion. But it 
was/is pretty useless to tell whether the file really contains 
extensions. So the safest way taken by FITS readers was to scan 
anyhow after the PHDU for named XTENSION kwds.

I doubt there are many readers around which won't do that is EXTEND is 
absent. 

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