ImageJ to remove Newton rings

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Radon86
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ImageJ to remove Newton rings

Post by Radon86 »

Hi All,
I am learning ImageJ to remove Newton Rings. Have had some success.
Would anyone be interested to know the details or has it already been covered in the past ?
Fast fourier transforms and reverse FFT could sort out problems that are not easily done at the image capture stage.

I am surprised this has not been posted here before.

Magnus


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Re: ImageJ to remove Newton rings

Post by Merlin66 »

Magnus,
Many of us have used similar techniques for the removal of NR in full surface solar Ha images.
I’m just completing trials with “plastic bag” diffusion filters for the full disk solar images.
Hope to upload soon.


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Re: ImageJ to remove Newton rings

Post by Montana »

I'm interested Magnus. I use a similar thing with a plug in for Photoshop called 'Pattern Suppressor'. It works very well most of the time but sometimes it just doesn't and I have no idea what it is doing. https://www.youtube.com/watch?v=FDM4lEw65j0

With the Chameleon + PST I have no luck with plastic bags, tilters, drift etc, this is the only thing which has made my images even basically nice.

Alexandra


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Re: ImageJ to remove Newton rings

Post by Radon86 »

Hi Alexandra,

Yes, I will go and research on Fast fourier transforms. ImageJ looks the most likely best bet, not sure if they have those plug ins for Photoshop.
It takes a bit of time to learn ImageJ properly, so I will give it a go and post when its ready. I believe the transformation is quite unbelievably good to remove NRs without too much image degradation or loss of detail or sharpness.

Magnus


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Re: ImageJ to remove Newton rings

Post by PDB »

Hi,

Think there is some filters for Photoshop with FFT.

Anyway it works with Gimp.

See this document I attached to an old solarchat post about Newton Rings:

download/file.php?id=31597

Regards,

Paul


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Re: ImageJ to remove Newton rings

Post by Radon86 »

Hello Paul,

:band

Thanks so much. Its as much as I could ever do I suppose.
I was not aware of GIMP being such a good way of removing NRs.

I was going to do a systematic thesis on them, and consider the various types of interference fringes, and how to apply ImageJ to best effect.
Well I will go and study your guide as it is really good.

Thanks!
Magnus


Solar: H-alpha": Quark Chromosphere filter; Baader white light filters
Scopes: Altair Astro Travel ED70mm (F 420mm, D=70mm);; Skywatcher 90mm (F 910mm D=90mm); GSO focuser;;Altair Astro 60mm guidescope (D=60mm,F=225mm)
Cameras: ASI120mm-S,ASI174mm
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Re: ImageJ to remove Newton rings

Post by Ivan »

Here is another photoshop plugin and a short tutorial https://m.youtube.com/watch?v=ortVtuiGZ ... e=youtu.be


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Re: ImageJ to remove Newton rings

Post by Radon86 »

Thank you Ivan.
I will study this closely.

What I was going to do, was to review some of the previous work and see how much ImageJ can contribute. I really wanted to understand how to remove NRs without it being a trial and error, hit and miss affair.
In other words, try to find a systematic way of analysing, removing NRs without compromising your original detail too much.

Maybe I will need more examples, so members could send in examples of their images with NRs (before processing), so I can work out a comprehensive solution to that.

I heard something about dispersion prisms to reduce or eliminate NRs. Where do you buy these ? I cannot find them.
Thanks a lot.


Magnus


Solar: H-alpha": Quark Chromosphere filter; Baader white light filters
Scopes: Altair Astro Travel ED70mm (F 420mm, D=70mm);; Skywatcher 90mm (F 910mm D=90mm); GSO focuser;;Altair Astro 60mm guidescope (D=60mm,F=225mm)
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Re: ImageJ to remove Newton rings

Post by Ivan »

The example I sent is not mine. This video was recorded by star-hunter, there is a link to his website.
There are many plugins for Photoshop that work as well, but in my opinion, they still leave barely noticeable traces that can be seen if you know where to look.
Of course, this is a great solution, but it does not work stably for me, i.e. it may turn out better or worse.
I haven't heard of dispersion prisms, and I'd be interested to know about them, too.


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Re: ImageJ to remove Newton rings

Post by FlankerOneTwo »

This has been suggested before as I recall and I've experimented with it somewhat as the PowerMates produce awful NR in my setups. I found it somewhat difficult to completely remove them cleanly with FFT and eventually gave up on it. Somewhat disappointing, as one would think that a frequency-domain approach should work well for them. I did find that the typical ZWO-type tilters did not produce enough tilt to remove the rings, the only thing that has worked reliably for me has been the Daystar Interference Eliminator, and I have to have it tilted pretty much all the way over to completely suppress the rings. The Baader telecentrics do not seem to produce NRs for me, so I've just switched to those for most things.

-Patrick


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Re: ImageJ to remove Newton rings

Post by Radon86 »

Hi Patrick,

I found ImageJ difficult at first. If you want me to try ImageJ on your troublesome image, I would be happy to try, it should only take a few minutes.

You could either post a reasonable size image (even less than 1 MB jpg could work or a small .tiff file).

Thanks.

Magnus


Solar: H-alpha": Quark Chromosphere filter; Baader white light filters
Scopes: Altair Astro Travel ED70mm (F 420mm, D=70mm);; Skywatcher 90mm (F 910mm D=90mm); GSO focuser;;Altair Astro 60mm guidescope (D=60mm,F=225mm)
Cameras: ASI120mm-S,ASI174mm
Mount: SW HEQ5 Pro, SW EQ3 Pro Synscan (SW = Skywatcher),Vixen Polarie tracker (portable setup)
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Re: ImageJ to remove Newton rings

Post by Merlin66 »

Magnus,
All the FFT type solutions I’ve seen seem to require basically an “even” NR pattern across the whole image, this is not always the case. E.g when imaging a full solar disk.
T2 tilters can help, but I’m finding “plastic bag” flats in FireCapture are working very well.


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Re: ImageJ to remove Newton rings

Post by FlankerOneTwo »

Boso36 wrote: Sun May 09, 2021 6:06 am Hi Patrick,

I found ImageJ difficult at first. If you want me to try ImageJ on your troublesome image, I would be happy to try, it should only take a few minutes.

You could either post a reasonable size image (even less than 1 MB jpg could work or a small .tiff file).

Thanks.

Magnus
Hi Magnus,

Thanks for the offer! I ultimately found it easier to eliminate the problem at the source, and the Baader telecentric and Interference Eliminator have so far been able to do the job.

-Patrick


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