Having Trouble with ISIS Image Subtraction Method?

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SUMMARY

The forum discussion centers on troubleshooting the ISIS image subtraction program developed by Alard, specifically addressing issues encountered during the PSF matching process. Users report a "Run error...Singular matrix in routine LUDCMP" when executing the ref.csh script. A solution was identified, which involves adjusting the default_config settings to ensure that pix_min is set to a lower value than min_stamp_center. This adjustment resolves the error and allows the program to function correctly.

PREREQUISITES
  • Familiarity with ISIS image subtraction software
  • Understanding of PSF (Point Spread Function) matching techniques
  • Basic knowledge of configuration file adjustments in software
  • Experience with shell scripting, particularly C-shell (csh)
NEXT STEPS
  • Review the ISIS image subtraction program documentation and tutorials
  • Learn about configuring parameters in ISIS, focusing on default_config settings
  • Investigate common errors in image processing software, particularly singular matrix issues
  • Explore advanced PSF matching techniques and their applications in astrophysics
USEFUL FOR

Astronomers, astrophysics researchers, and software developers working with image processing who are utilizing the ISIS image subtraction program for data analysis.

beavez
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Hi
I'm not sure if anyone here has used ISIS image subtraction program written by Alard, available online at http://www2.iap.fr/users/alard/package.html, but I'm hoping someone has.

I'm currently working on a bit of research that requires PSF matching to work, and this program should easily take care of that. However, I can't find any documentation other than his tutorial on how to use it.

That would be fine, as I have it installed, but it fails during the second step of the tutorial (the ref.csh) on my data.

Specifically, I get "Run error...Singular matrix in routine LUDCMP
Goodbye ! "

Here's hoping someone is able to help, it's driving me a bit insane. Thanks in advance!
 
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I had this same problem.
It seemed to be fixed when I made sure that, in default_config, pix_min had a lower value than min_stamp_center.
 

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