Supressing Newton Rings - Tutorial

[matt_baker]

Just found out how to suppress newton rings in a Ha Solar image and thought I'd share with you how

I tend to do this after all of my sharpening but you can do it before

I'm not sure about all the maths behind Fourier Transform but I know what to do

1. Download http://www.rognemedia.no/diverse/FFT.zip (It's an instant download)

2. Extract all but the .dll file into a folder in Plug-ins on Photoshop (typically located C:\Program Files (x86)\Adobe\Adobe Photoshop\Plug-ins) and call the folder FFT

3. Place the .dll file into the root directory of Photoshop

4. Load up Photoshop and change your colour to RGB using Image > Mode > RGB

5. Go to Filter > RONC 2018 > Ft2DH

It should do it's thing and come up with something like this

Now depending on how apparent your NR are, will depend on how easy they will be to see and suppress.

Mine aren't so apparent, so you have to look carefully for a bright speckle(s) around the star itself

In my case, although very hard to see are two brighter spots in the image

6. Paint over them in solid black with about the same diameter brush like this

7. Go back to Filter > RONC 2018 > Ft2DH and click on iFt2DH

8. Now hopefully your NR's are much less apparent or eliminated

Here's my before and after on my NR's:

Before:

After:

Hope this helps anyone

Edited April 30, 2020 by matt_baker

[Merlin66]

Matt,

The download link didn't work for me, but I found the site:

https://ft.rognemedia.no/

I'm not sure how effective this process is on solar images which only show "some" NR - not extending across the whole image.

Worth experimenting with????

(AstroArt also has a FFT filter, but it didn't work too well for me. I asked Fabio, and he said it (the FFT filter) only works where the fringes extend across the whole image. Bumma!)

 

Edited April 30, 2020 by Merlin66

[matt_baker]

11 hours ago, Merlin66 said:

Matt,

The download link didn't work for me, but I found the site:

https://ft.rognemedia.no/

I'm not sure how effective this process is on solar images which only show "some" NR - not extending across the whole image.

Worth experimenting with????

(AstroArt also has a FFT filter, but it didn't work too well for me. I asked Fabio, and he said it (the FFT filter) only works where the fringes extend across the whole image. Bumma!)

 

Sorry, I messed up spelling of the URL, has been changed now.

My NR actually didn't extend across the whole image, only certain bits of it, should've made it a tad more clear

Edited April 30, 2020 by matt_baker