Dark halo around objects after DBEor ABE

[manu.fonfon]

Good afternoon everyone

Although I am not a full beginner with Pixinsight, I am still fighting with it, sometimes. Hopefully, it gives great results most of tyhe time!

My current issue is the following:I sometimes get some dark halo around bright objects  (galaxies, stars) after applying DBE or ABE. Changing the settings does not really help and the only solution is to smoothen the histogram transformation in order to make the problem less visible.

Has anyone faced this problem already?

I attach an example (of course, I have exagerated the problem, to make it more visible...)

Thanks a lot!

[pfile]

this happens when you have samples on top of, or too near, the galaxy. when using DBE make sure there are no samples in the vicinity of the galaxy by deleting or moving them.

rob

[manu.fonfon]

Thanks Rob
But that's exactly what I did : whithout success (approx 2D, D being the "diameter of the galaxy)
But let's try again by removing even more
Emmanuel

[manu.fonfon]

In fact, what I did was to remove all sample points within the area corresponding to the "halo"...

[manu.fonfon]

Rob, indeed, I removed the sample points within an even larger area (3D?) and it worked fine!
Thanks for your help
Emmanuel

[wimvb]

There's rarely need to use more than about 10-12 samples in dbe. My usual approach to gradient removal is dbe with one sample in each corner, one along each edge, and a few sprinkled around the image, especially where I see a gradient. If you use too many samples, there's a risk that you start affecting weak signal, such as Ha dust or ifn. I also prefer large samples over small, increasing size from the default 5x5 pixels to 15x15 or larger.