Identify and WCS coordinates

nielbock wrote on Mar 10, 2006

Hi there,

I tried to calibrate my spectra with the "identify" task. I receive a strange error message saying:

"Warning: MWCS: cannot compile transformation, dependent axis has been excluded (world)"

What does this mean?

Cheers,
Markus.

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Mike Fitzpatrick wrote on Mar 10, 2006

Most commonly it means that there is an RA/DEC wcs in the image header which the spectral tasks like IDENTIFY can't handle. It can also happen when there is a dimension mismatch, e.g. the WCSDIM header keyword is '2' for a 1-D image or somesuch.

The solution is to remove the coordinate system from the header. You do this with

cl> wcsreset <images> wcs=world

Since the end result of most spectral data reductions is to dispersion calibrate the data the initial RA/DEC system is not needed. Hope this helps.

Cheers,
-Mike

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Last post on Mar 10, 2006