Avoiding Bright Spaces on the Sun

Discussions of using SharpCap for Solar or Lunar Imaging
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COSMOMOT
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Avoiding Bright Spaces on the Sun

Post by COSMOMOT » Sun Sep 17, 2017 11:35 pm

Do you know how can I avoid the 2 bright spaces on the surface of the Sun as it appears in the up right and down left off the attached picture?
Thank you!
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21587360_1425872370823765_8391088777254294360_o.jpg
21587360_1425872370823765_8391088777254294360_o.jpg (125.35 KiB) Viewed 112 times

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admin
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Re: Avoiding Bright Spaces on the Sun

Post by admin » Mon Sep 18, 2017 6:27 am

Hi,

I'm not really a solar imager, but the first thing to do is to reduce your exposure a bit so those areas are not saturated -that will make the image look more natural even if you can't get rid of them. I think the bright areas are caused by something in the optical system rather than the camera. It may be worth trying to apply flat frames to see if that helps, but that's just a bit of a guess. Hopefully someone who does more solar imaging will be along soon - if not it may be best to post in a general astronomy forum with a solar imaging section where more people will see your post.

cheers,

Robin

pipshag
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Joined: Sun Sep 10, 2017 7:52 pm

Re: Avoiding Bright Spaces on the Sun

Post by pipshag » Mon Sep 18, 2017 9:12 am

COSMOMOT wrote:
Sun Sep 17, 2017 11:35 pm
Do you know how can I avoid the 2 bright spaces on the surface of the Sun as it appears in the up right and down left off the attached picture?
Thank you!
Hello!

Using a simple solarfilter, I had the same view when capturing but after post processing got something like this. I almost thought it was a focus / exposure issue. Is it good enough? Then lower exposure and perhaps post process?
21753191_1973820799559388_4849242327003241885_o.jpg
21753191_1973820799559388_4849242327003241885_o.jpg (94.56 KiB) Viewed 109 times
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astrnmr
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Re: Avoiding Bright Spaces on the Sun

Post by astrnmr » Thu Sep 21, 2017 7:09 pm

The two areas that are bright are due to over exposure/glare in that region. Simply lower the exposure settings until the entire surface is displayed nicely in the view. You can always increase exposure in PS or other processing programs, but you cannot decrease something that is over exposed. I always start out with a really low exposure time and then gradually move up in exposure until the surface detail is quite nice and the surface over all is somewhat evenly illuminated.

Merlin66
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Joined: Fri Sep 15, 2017 4:20 am

Re: Avoiding Bright Spaces on the Sun

Post by Merlin66 » Mon Oct 02, 2017 12:52 am

Hmmm
The OP image is an Ha image (slightly out of focus..) and shows the typical "sweet spot" contrast which comes from the etalon tuning.
Try different tuning setting to see if you can find a compromise.
A flat using a thin plastic bag over the aperture can be used to correct the brightening.
Hope this helps.

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