fits extension syntax

[mgregg128]

The latest version of iraf appears unable to recognize the fits extension syntax of HST data, such as image.fits[sci,1] or image.fits[sci,2]. Is there a way to implement this? The workaround is to specify the absolute extension number of course (sci,2= extension 4 in most instances), but it would be handy to have the sci,n syntax work, if only to be able to use older scripts.

I'm running iraf 2.17 on a 2017 MBP with OS Ventura.

Thank you for the help,
Michael

[olebole]

The problem is that 2.17 accidently was configured to use the old image-open procedure. The best way is to update to version 2.17.1, which has this fixed (#236). Alternatively, you can fix this by adding these lines to unix/hlib/zzsetenv.def:

set	use_vo		= yes 
set	use_new_imt	= yes 

This will switch to the extended image-open procedure that allows to specify the MEF extension.

[mgregg128]

Thank you for the advice; I will try it.
I almost immediately also found that using all-caps works too, as in image.fits[SCI,1], which is recognized by iraf 2.17

[mgregg128]

I tried adding those lines to zzsetenv.def. This appears to have no effect.
If I issue the command:

imhead image.fits[sci,1]
iraf returns the message:
image.fits: FXF: must specify which FITS extension (image.fits)

But if I capitalize 'SCI', it works:
image.fits[1]{4096,2051][real]:

So I will upgrade to 2.17.1 next.
Thank you

[olebole]

If it doesn't work, the best here would as well be a small complete example that shows the problem.