Author Topic: Dark halo around objects after DBEor ABE  (Read 889 times)

Offline manu.fonfon

  • Newcomer
  • Posts: 7
    • View Profile
Dark halo around objects after DBEor ABE
« on: 2018 April 14 08:19:38 »
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!


Offline pfile

  • PTeam Member
  • PixInsight Jedi Grand Master
  • ********
  • Posts: 4464
    • View Profile
Re: Dark halo around objects after DBEor ABE
« Reply #1 on: 2018 April 14 10:35:49 »
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

Offline manu.fonfon

  • Newcomer
  • Posts: 7
    • View Profile
Re: Dark halo around objects after DBEor ABE
« Reply #2 on: 2018 April 14 12:55:38 »
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

Offline manu.fonfon

  • Newcomer
  • Posts: 7
    • View Profile
Re: Dark halo around objects after DBEor ABE
« Reply #3 on: 2018 April 14 12:59:19 »
In fact, what I did was to remove all sample points within the area corresponding to the "halo"...

Offline manu.fonfon

  • Newcomer
  • Posts: 7
    • View Profile
Re: Dark halo around objects after DBEor ABE
« Reply #4 on: 2018 April 14 13:26:08 »
Rob, indeed, I removed the sample points within an even larger area (3D?) and it worked fine!
Thanks for your help
Emmanuel

Offline wimvb

  • PixInsight Enthusiast
  • **
  • Posts: 91
    • View Profile
    • Wims place
Re: Dark halo around objects after DBEor ABE
« Reply #5 on: 2018 April 21 02:38:31 »
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.
Wim

AZ EQ6 GT + EQ3 PRO, SW 150P-DS, SW MN190, ZWO ASI174MM-Cool, Pentax K20D (retired),
SW ST80 + ZWO ASI120MM + Lin_guider