Re: Possibly wrong message is reported when a FITS image has only one HDU.

[Mohammad Akhlaghi]

Thanks a lot for bringing this to our attention.

I just defined bug #58363 [1], so we don't forget to precisely cite the 
part of the standard that encourages/recommends this. I cited a few 
parts of the FITS 4.0 standard about having metadata about the whole 
file in the primary HDU, but I'll have to find the exact part later ;-).

Generally, the point of the error message is not to say that the file is 
faulty. It just means to say something like this: "your data is on the 
primary HDU, so please run your command again with '--hdu=0', or '-h0', 
by default Gnuastro programs have '--hdu=1' or '-h1'.".

I just updated the description so it hopefully conveys this meaning and 
is less confusing:

http://git.savannah.gnu.org/cgit/gnuastro.git/commit/?id=61e44ed139

If you like you can get the latest Gnuastro version (with this commit 
implemented, currently version 0.11.60, or 60 commits after version 
0.11) from this link:

https://akhlaghi.org/gnuastro-latest.tar.lz
(I will shortly release version 0.12)

Thanks again for raising all these great points :-).

Cheers,
Mohammad

[1] https://savannah.gnu.org/bugs/?58363

On 5/12/20 9:26 PM, rmorales wrote:
> Summary:
> Possibly wrong message is reported when a FITS image has only one HDU.
>
> gnuastro version:
> 0.11
>
> test image set:
> https://cloud.iaa.csic.es/public.php?service=files&t=9344cdb85c640c7dd74446d8c266591d 
>
>
> command:
> aststatistics 019_00.fits
>
> result :
> ‘019_00.fits’ has only one extension/HDU but you have asked for the 
> second HDU (hdu number 1 in CFITSIO) ....
> …
> Gnuastro leaves the first HDU blank (with no data) and writes the 
> outputs in the second HDU.
> ...
> This is the recommended way in the FITS standard.
> ...
>
> question:
> Maybe I’m wrong, but I did not find any recommendation in the last FITS 
> standard to organize the FITS file in that way.
>
> FITS standard: Version 4.0 (13 August 2018)
> https://fits.gsfc.nasa.gov/standard40/fits_standard40aa-le.pdf
> Section 3. FITS file organization
>
> Using fitsverify also does not report any error or warning on the same 
> file.