Help: How to remove noise ring in an image

ttrinko

Member
Nov 9, 2017
13
0
the attached image uses 3 300second luminosity images and one each 300 second Red Green Blue image.

While I've been using Pixinsight for awhile I just do basic things ABE, BN, CC and histogram correction.

So I don't know how to deal with the noise ring I'm seeing, which is strongest in the R frame.

I could select the region and drive down the signal until the noise is black but that gets rid of the real signal in the region.

Is there some way in Pixinsight to eliminate the noise band--actually it's probably caused by some optical defect or an external light source--without eliminate the actual scene signal?

Thanks for any help!
 

Attachments

srecaldin

Member
Jul 6, 2017
14
1
Are you really confident that your calibration frames are correct? It is just that I would have thought that noise would be more random than this. I can remember when "Chuck's Astrophotography" had something very similar he troubleshooted to the calibration frames.
 

John_Gill

Well-known member
May 6, 2016
465
19
62
Durban, South Africa
I think the "flats" are to blame and then the background extraction (DBE/ABE). Have a close look at the flats and the results after ImageCalibration.
The core of Orion is very saturated and that might also have some impact on the bright ring .... hope this helps.
 

JPetruzzi

Active member
Jun 18, 2020
40
9
I've seen that "ring" effect when ABE is used with too high a function degree. I tend to use DBE more, but when I use ABE I start with a function setting of 2, the default of 4 is often too high in my (limited) experience.
 

ttrinko

Member
Nov 9, 2017
13
0
I let iTelescope do the calibrating so I'll go and get the calibration frames and see if that makes a difference

Also I'll try DBE

Thanks!
 

ttrinko

Member
Nov 9, 2017
13
0
So fortunately I didn't need to recalibrate the frames.

Using DBE instead of ABE solved the problem so thanks everyone!

Unrelated question: How do I use Pixinsight to get an HDR image so that the core of Orion isn't oversaturated?

Thanks!
 

JPetruzzi

Active member
Jun 18, 2020
40
9
Glad DBE did the trick....again, sometimes ABE works fine, you just need to reduce the function degree. To answer your other question, there's a few ways. You can produce master files at two different exposure levels and combine them using HDR Composition, or with a single image try using HDR Multiscale Transform, play with the settings and see what you get. :)