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Bringing out coronal loops- Sean Walker Method

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#1 Starry_Spruce

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Posted 09 April 2024 - 09:53 PM

Hi all.

 

I am now sitting on some nice eclipse data with little experience in processing. I have photoshop and associated programs (adobe camera raw). 

 

My goal at the moment is stacking bracketed images and trying to bring out coronal loops, maybe some earthshine. I am following this tutorial from Sean Walker at Sky&Telescope:

https://skyandtelesc...otality-in-hdr/

 

I have gotten most the way through, but his tutorial seems to peter out a bit near the end when he talks about getting rid of the 'ring artifact' and bringing the moon back in. Specifically, in the second to last chunk of text between images, he says:

"When you’ve circled it all, choose Select > Inverse from the dropdown menu and hit the backspace key on your keyboard. When you change the layer blending mode back to Normal, the bright ring should be reduced to a thin line."

 

When I select inverse and then hit backspace, literally nothing happens. And where I pasted the square crop of the moon, it does not blend in well at the edges of the crop. I'm not sure if the steps he discusses afterwards somehow gets rid of these, but he really doesn't offer much more guidance...

 

So for those familiar with this process, any hints?

 

Alternatively, any other good tutorials for bringing out the loops on stacked bracketed images?



#2 agavephoto

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Posted 09 April 2024 - 10:09 PM

Also look into the Larson-Sekanina filter for this as another alternative: this is what I used for my 2017 corona HDR imaging. PixInsight has this filter, and I'm sure other software packages do, too. 



#3 Starry_Spruce

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Posted 09 April 2024 - 10:53 PM

Ok thanks, I'll check that out.

 

I'm able to get the corona looking halfway decent as you can see below, but the moon is a mess (has a big black line artifact and I'm also unable to draw out the earthshine despite having plenty good data of it in the original stack). 

 

Bracket series 1 loops ACR

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#4 Starry_Spruce

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Posted 10 April 2024 - 11:32 PM

Well I've given up on Sean's method for the time being.

The radial blur filter doesn't mess with the moon the same way, and thus is easier to use. Still bringing the moon back in afterwards  but at least no thick black line artifact. 

 

Getting decent results with it (below), though I do think the gaussian blur Sean uses maybe has a slight edge in terms of corona quality.

 

Series 2 aligned to stars radial whiter

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#5 swalker

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Posted 02 May 2024 - 06:24 AM


 Specifically, in the second to last chunk of text between images, he says:

"When you’ve circled it all, choose Select > Inverse from the dropdown menu and hit the backspace key on your keyboard. When you change the layer blending mode back to Normal, the bright ring should be reduced to a thin line."

 

When I select inverse and then hit backspace, literally nothing happens. And where I pasted the square crop of the moon, it does not blend in well at the edges of the crop. I'm not sure if the steps he discusses afterwards somehow gets rid of these, but he really doesn't offer much more guidance..."

 

 

It's hard to tell what step you are missing, but many others have used my description successfully without hitting a road block at this step.. Make sure you have selected the correct layer before inverting the selection and deleting it. Afterwards, you probably will need to adjust the levels or curves until the layer matches the outer corona layers. And of course, the Moon still will need to be layered in separately.

 

Sometimes, Photoshop runs out of RAM with these many-layered images, and tools stop working as they should. You may simply need to restart the program and continue at this point. again.

 

While  processing the image entirely using the radial blur method makes a nice image, it ignores the loops that are parallel to the Moons edge. It's a subtle but important difference.

 

 

 

 


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#6 swalker

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Posted 02 May 2024 - 06:55 AM

Well I've given up on Sean's method for the time being.

The radial blur filter doesn't mess with the moon the same way, and thus is easier to use. Still bringing the moon back in afterwards  but at least no thick black line artifact. 

 

Getting decent results with it (below), though I do think the gaussian blur Sean uses maybe has a slight edge in terms of corona quality.

 

Looks like you have excellent data, and that's a fine result. I didn't catch earthshine this year due to light clouds causing scatter around the lunar limb in the longer exposures. Not to mention... my tracking mount died just before totality, so I had to limit my exposures to less than 1 second. 


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#7 Starry_Spruce

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Posted 02 May 2024 - 09:13 AM

Hi Sean,

 

Wow thanks for responding here! And thanks for your original tutorial. You are right, the loops parallel to the moon's edge are brought out much better with your method. 

 

I just tried it again and it worked! I am pretty new to photoshop so I imagine I either had the wrong layer selected, or something like that... not really sure to be honest. I did also recently upgrade my RAM and SSD because I've learned pretty quick how intensive this image processing is.

 

I was in Maine which had supremely clear skies. Sorry to hear about your mount dying! I was skeptical it would all come together for me (using Eclipse Orchestrator) but it pulled through. Great experience. 

 

I'll give your method another go here.


Edited by Starry_Spruce, 02 May 2024 - 09:14 AM.

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#8 swalker

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Posted 02 May 2024 - 10:45 AM

My pleasure, and glad you got it to work. Looking forward to your final version!

I posted my result in the solar eclipse viewing forum.



#9 Daniel Dance

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Posted 02 May 2024 - 04:00 PM

First of all, if you're only processing one camera / focal length, you're not going to get those crazy lengthy corona images you see posted.  You know the types - the fancy HDR images. 

Those images are composites of different focal lengths, LOTs of bracketing, and LOTs of exposures. 

 

 

But as long as you have multiple bracketed exposures, then you have a chance to get something decent assuming you had perfectly clear skies.  High level clouds really mutes any detail and faint extensions in the corona.

 

Just remember, the images you THINK are OVEREXPOSED, are actually the images that have the best data for your corona!!!!!  Composite them with short exposures.





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