Star "Ringing" Artifact - Forums

Topic starter

Aug 21, 2024

Hello Astrobin,

I have been working on a new setup, and slowly working through growing pains. The setup is as follows:

Stellarvue SVX90T w/Field Flattener>Spacers to achieve proper back focus>Falcon Rotator V2, EFW (36mm Chroma LRGB + 5nm SHO), 2600mm attached directly to EFW

One issue I am noticing is that all medium/bright stars have a "ringing" type artifact as depicted below. I have tried flipping the filter orientation, with no noticeable difference. There is various posts on Cloudy Nights and other forums with this issue or similar and Chroma filters, but no smoking gun solution. I continue to highly suspect the filters, but I am honestly not sure.

Photo link/description:
Top row = Reflective side of filter facing telescope
Bottom row = Reflective side facing camera
Each row arranged L-R-G-B-S-H-O (top row missing S&O)
LRGB = 20x5" stacked images
H = numerous 240" stacked images
S&O = single 240" subs

Other notes:

I see the ringing in individual frames and with various exposure lengths as well, not presented here. So, I don't think it's Pixinsight introducing it.
Luminance seems ok.
While Sadr is presented in most of my examples, it occurs in all medium/bright stars all throughout the FOV.
Chroma states filter orientation doesn't matter (but swap if it does).

Does anyone recommend any troubleshooting steps from here? I have e-mailed Chroma, and I am awaiting a response.

Thank you!

Chris

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andrea tasselli

Frequent contributor

Aug 21, 2024

Ah, the Onion Rings effect. Interference driven thingy. Getting other filters would be the easiest path out of it, tbh. Refractors seem mostly affected by this unless very high end so maybe there is a clue somewhere there too…

Bob Lockwood

Aug 21, 2024

Get with Stellarvue and send them this pic, I'm sure Vic can tell you what's going on

apennine104

Topic starter

Aug 21, 2024

andrea tasselli:
Ah, the Onion Rings effect. Interference driven thingy. Getting other filters would be the easiest path out of it, tbh. Refractors seem mostly affected by this unless very high end so maybe there is a clue somewhere there too...

I thought the onion ring effect was only related to fast food consumption

. Hmm.. your response gave me the idea of maybe undergoing the process of swapping the filters between my two EFWs/setups to see if that "fixes" the problem by just putting them in a different optical setup. I will see what Chroma recommends.

-Chris

apennine104

Topic starter

Aug 21, 2024

Bob Lockwood:
Get with Stellarvue and send them this pic, I'm sure Vic can tell you what's going on

Thanks, I have done that too. They have been great to work with.

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Maciej Karcz

Aug 21, 2024

I use a SVX102T and also keep getting onion ring stars on all medium/bright stars.
I had some back and forth with Stellarvue and have been troubleshooting this issue for about a year. I get so few clear nights that it's been slow going to troubleshoot.
Stellarvue has been pretty helpful and the asymmetric onion rings I had initially were due to a backspacing issue, but once that was solved I started getting symmetric onion rings instead.

Initially I thought it was due to their .74 reducer and switched to their flattener but the issue persisted. I started out with ASI2600MC with Optolong filters and later moved to 2600MM with Antlia 3nm but the issue is still there, so I don't think it's a camera or filter issue.

SVX102T with reducer and 2600MC / Optolong L-Pro, all bright stars had rings: M45

SVX102T with flattener and 2600MM with Antlia 3nm SHO + RGB, see red giant Propus at bottom left: Jellyfish Nebula

My post from 1.5 years ago with mostly asymmetric onion rings: here

Regards,
Maciej

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apennine104

Topic starter

Aug 21, 2024

Maciej Karcz:
I use a SVX102T and also keep getting onion ring stars on all medium/bright stars.
I had some back and forth with Stellarvue and have been troubleshooting this issue for about a year. I get so few clear nights that it's been slow going to troubleshoot.
Stellarvue has been pretty helpful and the asymmetric onion rings I had initially were due to a backspacing issue, but once that was solved I started getting symmetric onion rings instead.

Initially I thought it was due to their .74 reducer and switched to their flattener but the issue persisted. I started out with ASI2600MC with Optolong filters and later moved to 2600MM with Antlia 3nm but the issue is still there, so I don't think it's a camera or filter issue.

SVX102T with reducer and 2600MC / Optolong L-Pro, all bright stars had rings: M45

SVX102T with flattener and 2600MM with Antlia 3nm SHO + RGB, see red giant Propus at bottom left: Jellyfish Nebula

My post from 1.5 years ago with mostly asymmetric onion rings: here

Regards,
Maciej

Maciej, thank you for your response. I had not seen your post before, even though I did a lot of searching. I also just found this post on Cloudy Nights which seems to be the same problem.

Chroma responded that they think it "may be attributable to multiple reflections between sensor window (or the flattener) and our filters". That seems plausible to me. I also have had a string of bad weather that has made this slow going. I think unless Stellarvue provides a different path, I am going to swap my filters (Chroma for ZWO) and see if the issue remains.

-Chris

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apennine104

Topic starter

Aug 25, 2024

Well, I swapped in the ZWO filters, and the onion stars were not fixed. Similar to @Maciej Karcz's experience.

I don't think the issue is with the 2600MM, since the luminance is fine. I am suspecting something with the telescope. I am waiting for more info from Stellarvue. Please let me know if anyone has further thoughts/info!

20x5" per filter L-R-G-B:

Thank you!

-Chris

TiffsAndAstro

Aug 25, 2024

Is there any option to move filter further from your sensor?

Tony Gondola

Frequent contributor

Exemplary contributor

Aug 25, 2024

This is prob. way off but the third image from the right really looks like the posterization effect you get when you don't have enough bits to show the full brightness range.

andrea tasselli

Frequent contributor

Aug 25, 2024

Well, I swapped in the ZWO filters, and the onion stars were not fixed. Similar to @Maciej Karcz's experience.

I don't think the issue is with the 2600MM, since the luminance is fine. I am suspecting something with the telescope. I am waiting for more info from Stellarvue. Please let me know if anyone has further thoughts/info!

20x5" per filter L-R-G-B:

Thank you!

-Chris

Luminance filter isn't an interference filter so that is to be expected. Hard to find the right ones, I'm afraid.

apennine104

Topic starter

Sep 1, 2024

The telescope/flattener is on its way back to Stellarvue. I'll update when I get this solved, thanks everyone!

-Chris

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apennine104

Topic starter

Oct 18, 2024

Quick update to close the loop: A new objective lens installed by Stellarvue fixed the "ringing/onion" issue.

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Maciej Karcz

Oct 21, 2024

Thanks for the update @apennine104 . I may need to do the same with my SVX102T, just not looking forward to the shipping headache..
Did they provide any explanation other than replacing the lens?
How long was the turnaround time? Did Stellarvue cover shipping?

apennine104

Topic starter

Oct 22, 2024

Maciej Karcz:
Thanks for the update @apennine104 . I may need to do the same with my SVX102T, just not looking forward to the shipping headache..
Did they provide any explanation other than replacing the lens?
How long was the turnaround time? Did Stellarvue cover shipping?

Hi Marciej, they did not explain further, only that it would undergo an evaluation at a later time. I'm on the East Coast, so it was about a week each way, then two weeks at their facility. So, about a month. Stellarvue was great to work with, and they covered shipping in my case. I am not sure if shipping was covered because I had ordered so recently, but they definitely made the process painless.

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