[iaufwg] Appendix A, END keyword

[William Pence]

Steve Allen wrote:
> On Thu 2008-03-20T17:42:23 -0400, William Pence hath writ:
>> The END keyword on the other hand is prohibited from having an '= ' in
>> bytes 9-10, so it is not necessary to make it as a special case in this
>> grammar.
> 
> I regret to admit that, among other mistakes, despite it always having
> been illegal, there are FITS files written at Lick which have a "="
> character following "END     ".

Unfortunately this is not unusual, and many observatories are currently 
still distributing FITS files that violate the FITS Standard.   We 
should try to encourage more projects to make use of existing tools, 
such as the FITS file verifier at 
http://fits.gsfc.nasa.gov/fits_verify.html to check their FITS files 
before archiving and distributing them.  Once invalid FITS files get 
archived, it is often difficult for projects to find the resources to go 
back and fix them.

In my experience, most, if not all, of the common errors seen in FITS 
files are clear violations of the original FITS definitions and are not 
a result of changes to the FITS requirements that retroactively caused 
existing FITS files to become invalid.  The one case of a new 
requirement that is commonly cited, i.e., the change made back in 1999 
to *require* rather than only *strongly recommend* that the keyword 
value and comment field be separated by a slash character, is largely a 
non-issue, I think, because I can't remember ever seeing a FITS file 
that doesn't follow this convention.  Even if there are some FITS files 
created before 1999 that don't have the slash character separator, this 
is the sort of minor infraction that most FITS reading software would 
ignore anyway.

Bill
-- 
____________________________________________________________________
Dr. William Pence                       William.Pence at nasa.gov
NASA/GSFC Code 662       HEASARC        +1-301-286-4599 (voice)
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