I'm trying to convert a near-infrared spectrum from the SpeX instrument on IRTF so that I can (de)redden it using the task DEREDDEN. I have an ASCII text file of the reduced SpeX spectrum, and I've converted it two different ways for IRAF ingestion:

(1) Via SINTERP
(2) Via RSPECT

In either case, the spectrum looks fine, and I'm able to SPLOT it without issues. The trouble comes when I try to run DEREDDEN itself. Here is my parameter file for that task:

input = try1.fits Input spectra to correct
output = junk.fits Output corrected spectra
value = -1. Extinction parameter value
(R = 3.1) A(V)/E(B-V)
(type = A(V)) Type of extinction parameter
(apertur= ) Apertures to correct
(overrid= no) Override previous correction?
(uncorre= no) Uncorrect previous correction?
(mode = ql)

If I use either spectrum as an input, I get the same error message --

Warning: Image header parameter not found (EXTVER)

I've even tried adding in the EXTVER=1 keyword into the header using HEDIT, but even after I do this I get the same Warning message. Here's the full screen output:

on> dered
Input spectra to correct (try1.fits):
Output corrected spectra (junk.fits):
Extinction parameter value (-1.):
Warning: Image header parameter not found (EXTVER)
[junk.fits]:
Oct 16 19:11 A(V)=-1. R=3.1
Ap 1:

Any help debugging this would be most appreciated!

---Davy Kirkpatrick

See the post at http://iraf.net/phpBB2/viewtopic.php?t=83415&highlight=deredden+extver for hints. The EXTVER error is basically a quirk of the system that means there is some other error (e.g. a missing header keyword, some other trapped error) but when the task tries to clean up the wrong error message is substituted before the task exits. Note the limits on the wavelength range over which the task works (1000-30000A) and be sure you've got things like the DC-FLAG keyword in the header. The SLIST task should tell you whether/what IRAF thinks the dispersion is, otherwise please post a complete header (e.g. "imhead spec.fits long+").

Cheers,
-Mike