Gray Halo Around Stars

Questions and answers about processing in StarTools and how to accomplish certain tasks.

Gray Halo Around Stars

Postby juno16 » Thu Jan 02, 2020 1:49 am

Hi and Happy New Year!

I see this effect sometimes in my images and I haven’t had success correcting it in Startools.

Sometimes, the bright stars (maybe all, but less evident in the smaller stars) have gray halos surrounding them. It takes a lot of the snap out of the image because it gives a “blurry” look.

Please see the image below.

8C7EFECA-5047-451A-A6B4-9AD073B743FB.jpeg
8C7EFECA-5047-451A-A6B4-9AD073B743FB.jpeg (114.65 KiB) Viewed 620 times


I thought it was saturation, but the smaller stars have the effect also.

Is there a module/mask combination that might rectify the effect?

I am imaging with a Ha modified Nikon D5300.

Thanks,
Jim
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Re: Gray Halo Around Stars

Postby juno16 » Thu Jan 02, 2020 2:38 pm

I uploaded two images to Google Drive.

One is the full tiff image that was used to crop the image in the original post. https://drive.google.com/file/d/1brvf2x ... sp=sharing

The second is a tiff from a drizzle stacked version what shows the star halo a bit more. https://drive.google.com/file/d/1nrJQbr ... sp=sharing

Thank you for any ideas that you can offer!

Jim
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Re: Gray Halo Around Stars

Postby happy-kat » Thu Jan 02, 2020 7:34 pm

Are you using a Ha filter with your modded camera?
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Re: Gray Halo Around Stars

Postby juno16 » Thu Jan 02, 2020 8:29 pm

Hi Happy-kat,

Thanks for the reply.

I recently had the camera Ha modified by Lifepixel. They removed the stock IR filter and installed an Ha filter. I did not have a full spectrum mod ( I know that I would need a UV/IR cut filter for that).
Possible bloating? Maybe, but I have shot several other targets since the mod and they look good. Even Pleiates with no issue with the stars. I shot the Flaming Star Nebula the same night and even though it was buried in lp, I didn’t see the issue there ( or not as prominent).

Any ideas how to control or reduce the halo in Startools?

Thanks,
Jim
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Re: Gray Halo Around Stars

Postby happy-kat » Fri Jan 03, 2020 10:32 am

Perhaps that night's seeing was bad when you took the image if other bright stars on other nights are not doing the bloat.
Maybe some of the chromatic aberration tweaks would help.
viewtopic.php?f=6&t=924&start=10
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Re: Gray Halo Around Stars

Postby juno16 » Sat Jan 04, 2020 1:53 pm

Hi happy-Kat,

I posted also to the forum that I am a member of too (The Sky Searchers).

Some posts mentioned what you hit on in your first reply. Possible bloating because of the extended Ha response. Also, some over-stretching exaggerated the problem.

I appreciate the link. Some good and useful info there. Since my particular issue was a gray halo and not blue, I used some of the techniques (including a man dev) to improve my halo issue some.

031C89BD-4218-4813-AFC8-A8AFE9F33BFE.jpeg
031C89BD-4218-4813-AFC8-A8AFE9F33BFE.jpeg (162.51 KiB) Viewed 537 times


Much better!

I did order a filter to help with the bloating.

Thanks a lot for the guidance!

Jim
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Re: Gray Halo Around Stars

Postby happy-kat » Sun Jan 05, 2020 7:00 pm

That's a tidier process.
Re filter I was wondering if the Ha was through using a filter and that had reflection issues and was causing the bloating on bright stars if it was every imaging session.
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Re: Gray Halo Around Stars

Postby Rkonrad » Sat Jan 11, 2020 8:08 am

Hi Jim,

If you would like to share us your linear stacked data, I could have a go and see what I could offer.

Cheers Richard
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Re: Gray Halo Around Stars

Postby RICH-DSO » Sat Jan 25, 2020 2:45 pm

I have had this issue of grey halo and I resolved it by making the star mask tighter to the stars.
I make sure to never use a mask with Life module, problem solved.


Compare these two images
https://www.astrobin.com/6zres6/0/?nc=user

And this one


https://www.astrobin.com/6zres6/C/?nc=user

The grey halo will be an issue even with Ha filter or any filters...

Clear skies
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Re: Gray Halo Around Stars

Postby juno16 » Mon Jan 27, 2020 3:16 am

Rkonrad wrote:Hi Jim,

If you would like to share us your linear stacked data, I could have a go and see what I could offer.

Cheers Richard


Hi Rkonrad,

Sorry about the late response. If you are still available, here is an image that I shot a few night ago. The large central star in ngc 2174 has a pretty big halo. Other bright stars have blue halos too. Attached is the linear jpg processed file. Is that what you are asking for? Or, do you want a link to google drive to the unstretched fits file?

Thanks for your help!

Jim
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