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I could not find this topic in the general help section so I hope this isn't a repeat. I get a 'floating point invalid operation' error when flat fielding an image using CCDPROC. Below is my epar ccdproc. This error occurs with and without the trimsec parameter given.

images = justfibers/0290.double.fits List of CCD images to correct
(output = justfibers/0290.zdouble.fits) List of output CCD images
(ccdtype= none) CCD image type to correct
(max_cac= 0) Maximum image caching memory (in Mbytes)
(noproc = no) List processing steps only?

(fixpix = no) Fix bad CCD lines and columns?
(oversca= no) Apply overscan strip correction?
(trim = yes) Trim the image?
(zerocor= yes) Apply zero level correction?
(darkcor= no) Apply dark count correction?
(flatcor= yes) Apply flat field correction?
(illumco= no) Apply illumination correction?
(fringec= no) Apply fringe correction?
(readcor= no) Convert zero level image to readout correction?
(scancor= no) Convert flat field image to scan correction?
(readaxi= line) Read out axis (column|line)
(fixfile= ) File describing the bad lines and columns
(biassec= ) Overscan strip image section
(trimsec= [1:500,1:1100]) Trim data section
(zero = justfibers/Zero.fits) Zero level calibration image
(dark = ) Dark count calibration image
(flat = justfibers/Flat.fits) Flat field images
(illum = ) Illumination correction images
(fringe = ) Fringe correction images
(minrepl= 1.) Minimum flat field value
(scantyp= shortscan) Scan type (shortscan|longscan)
(nscan = 1) Number of short scan lines

(interac= no) Fit overscan interactively?
(functio= minmax) Fitting function
(order = 1) Number of polynomial terms or spline pieces
(sample = *) Sample points to fit
(naverag= 1) Number of sample points to combine
(niterat= 1) Number of rejection iterations
(low_rej= 3.) Low sigma rejection factor
(high_re= 3.) High sigma rejection factor
(grow = 0.) Rejection growing radius
(mode = ql)

An 'invalid operation' error is a generic floating point error message but doesn't sound familiar. These are sometimes data related so it would help if you could upload the problem image to the anonftp at ftp://iraf.noao.edu/pub and let me know what IRAF version and platform you are running so we can reproduce it. You might also check for an unusually large number of zero values in the image, or that your header keywords are correct (e.g. there was an old problem that would trigger this error is the 'darktime' keyword was absent or not found in the translation).

The problem may also be a bug in the task, e.g. use of uninitialized memory or some 64-bit problem, however there are no known problems like this at the moment. Hope this helps.

I am using v2.16 of IRAF on Fedora 3.10. I will try to upload the files I am working with shortly.

I believe I have uploaded

0290.double.fits
Flat.fits
Zero.fits

to ftp://iraf.noao.edu/pub

Thank you.

I will also try to run it again trimming out more of the image to see if its a having too many zeros problem.

I believe that trimming more of the image to fit my data got rid of the error. Thank you so much for suggesting that as an issue. If you think there may be other issues going on please let me know. Otherwise, thanks for all your help!

I was able to reproduce the problem but found that it happened when trying to open the 'instrument' parameter file, which was never actually set. Did you specify an instrument or use the SETINSTRUMENT task?

No. I never set that parameter. Not sure where that comes into CCDPROC.

In most cases you would run the SETINSTRUMENT task to define a header translation so that e.g. the exposure time keyword is what is actually in your data. See for instance the CCDPROC overview at https://iraf.net/irafdocs/ccduser3.pdf

I don't think I've ever used that before with ccdproc. Haha. Learn something new everyday I guess.