DBE Fails for an image

[better]

On a relatively normal-looking image of M33, DBE is failing with:

"This DynamicBackgroundExtraction instance has less than three background samples defined."

I have tried the suggestions found on other posts:
  1. Increasing the Tolerance. I bumped it all the way to to its maximum of 10.
  2. Increase Shadows relaxation.

For some reason, every sample point appears red in the sample viewer and so the Wg and Wb are 0.000 for every point, regardless of what I set the Tolerance to. However, the actual G and B pixel values are NOT zero; they seem to be normal values.

Can someone help me understand what's wrong with this image? DBE works fine on other images.

[niteman1946]

Hi better,

This may or may not help, but....

I would dynamic crop the image prior to DBE.  This eliminates all the overlap around the boarders, and may fix your problem.

Mark

[better]

Thanks for the quick reply, Mark. That fixed the DBE issue!

[pfile]

cropping helps the statistical analysis of the image. the borders sometimes fool the computation.

however, even with cropped borders you may find bad samples. they should turn red. the way to fix this is to futz with the threshold and the background relaxation parameters.

rob