TECH QUESTION FOR SOLAR PHOTOGRAPHY EXPERTS
When I photograph the Sun, whenever I process in imPPG, to get any kind of clear prominence, end up also getting my limb processing too dark (or too bright, when I invert), without natural smooth transition across the limb.
How do I avoid this? Please explain, and if you have screenshots of imPPG curves, that would help.
Thank you!
I am not a solar expert but my guess from what little I know, is that the longer exposure to needed for the prominences also picks up the fainter part of limp, slightly extending it outward. I see this in a lot of solar Ha images and I suspect it has something to do with how narrow the filter band is. No idea what the processing fix is. I’m hoping the solar guys here will jump in on this thread.
Its been a while since I used ImPPG for solar (the astrobin user GreatAttractor should be the best person to answer that I suspect).
But if you have PI, you can also try the Solar Toolbox that Bill Blanshan and Mike Cranfield have put together. There if you choose the setting for solar limb, that controls the way the limb edge ends up being processed.
Thank you
The astrobin user GreatAttractor is the guy who makes the program. I’m not going to bug him with that. I’ve already asked him for feature requests (that he says he may implement.)
I have SolarToolbox too, I use it only for orange coloring with one click. When I do processing with it, the Sun always seems “overbaked.” I guess I should work with the settings more than the little I have.
But I know this is an issue with imPPG settings, I just don’t know what to change. I think imPPG is the way to approach it, since it’s the classic main program used for this.
Good reply though.
Not an expert by any means but I have been doing daily solar Ha for about a month and this is what I do:
1) set up an lucky imaging sequence with normal exposure so that none of the plage regions are blown out.
2)After stacking this in AutoStakkert4
3) I sharpen and brighten (if needed) resulting stack in IMPPG.
4) Bring the sharpened image into Photoshop and duplicate it,
5) copy one of the images into the other so that there are two layers.
6) Name one layer Surf and the other Prom. I put Surf on top and Prom on the bottom.
7) draw a tight circular selection around the solar disk of Surf with a feather appropriate to your image scale ( for my Player One Saturn SQR with 1.25x Barlow its 5 pixels), then make the selection a mask.
8) Now a curves adjustment layer can be used to brighten the prominences without affecting Surf.
If you dont have PS, other photo processors (GIMP) have same layer and masking capabilities
I used to take two separate exposures, one normal and one exposed for proms, but realized that a normal exposure still contains enough prom data that that they can be resurrected by using curves. Its been my experience that the limb looks more natural using one exposure than dealing with minor differences that are inherent in two separates.
dan baldwin · Jun 7, 2026, 03:01 PM
Not an expert by any means but I have been doing daily solar Ha for about a month and this is what I do:
1) set up an lucky imaging sequence with normal exposure so that none of the plage regions are blown out.
2)After stacking this in AutoStakkert4
3) I sharpen and brighten (if needed) resulting stack in IMPPG.
4) Bring the sharpened image into Photoshop and duplicate it,
5) copy one of the images into the other so that there are two layers.
6) Name one layer Surf and the other Prom. I put Surf on top and Prom on the bottom.
7) draw a tight circular selection around the solar disk of Surf with a feather appropriate to your image scale ( for my Player One Saturn SQR with 1.25x Barlow its 5 pixels), then make the selection a mask.
8) Now a curves adjustment layer can be used to brighten the prominences without affecting Surf.
If you dont have PS, other photo processors (GIMP) have same layer and masking capabilities
I used to take two separate exposures, one normal and one exposed for proms, but realized that a normal exposure still contains enough prom data that that they can be resurrected by using curves. Its been my experience that the limb looks more natural using one exposure than dealing with minor differences that are inherent in two separates.
Fascinating and I’m going to try it. Thanks!
Did you do that on all 3 still images of the Sun of yours on here? The rest are animations, I’m guessing you didn’t do it on there?
If not all 3, can you tell me which of your images on here you did with this technique?
Someone else suggested also shooting at a lower gain. I’m at 75 percent histogram, maybe I should try 70 or even 65.
Michael W. Dean · Jun 7, 2026 at 02:37 AM
Thank you
The astrobin user GreatAttractor is the guy who makes the program. I’m not going to bug him with that. I’ve already asked him for feature requests (that he says he may implement.)
I have SolarToolbox too, I use it only for orange coloring with one click. When I do processing with it, the Sun always seems “overbaked.” I guess I should work with the settings more than the little I have.But I know this is an issue with imPPG settings, I just don’t know what to change. I think imPPG is the way to approach it, since it’s the classic main program used for this.
Good reply though.
“makes the program” are you talking about IMPPG ? Thats a phenomenal piece of software.
dan baldwin · Jun 7, 2026, 03:36 PM
The astrobin user GreatAttractor
Yes.
The AstroBin user GreatAttractor is the developer of imPPG.
Check out his DIY 10” solar Newt:
https://solarchatforum.com/viewtopic.php?t=49359
(Has an un-coated primary mirror, like most / all Newts that are made to not catch their cameras on fire. lol)
Tony Gondola · Jun 6, 2026, 04:30 PM
I am not a solar expert but my guess from what little I know, is that the longer exposure to needed for the prominences also picks up the fainter part of limp, slightly extending it outward. I see this in a lot of solar Ha images and I suspect it has something to do with how narrow the filter band is. No idea what the processing fix is. I’m hoping the solar guys here will jump in on this thread.
Someone who’s much more experienced at solar told me today that it’s the opposite. Need less light (lower gain) to be able to get data that can differentiate regions better in processing.
I’m shooting with my histogram at 75 percent. Next time I’ll try 70 and 65 percent. (maybe shoot each area at 70, 65, and 60, and type which one is which)
And also will use Highlight Over Exposed in SharpCap Pro. (I just learned of it)
If only that tool could be used more persistently! I just did a feature request for that:
Michael W. Dean · Jun 7, 2026 at 03:10 PM
dan baldwin · Jun 7, 2026, 03:01 PM
Not an expert by any means but I have been doing daily solar Ha for about a month and this is what I do:
1) set up an lucky imaging sequence with normal exposure so that none of the plage regions are blown out.
2)After stacking this in AutoStakkert4
3) I sharpen and brighten (if needed) resulting stack in IMPPG.
4) Bring the sharpened image into Photoshop and duplicate it,
5) copy one of the images into the other so that there are two layers.
6) Name one layer Surf and the other Prom. I put Surf on top and Prom on the bottom.
7) draw a tight circular selection around the solar disk of Surf with a feather appropriate to your image scale ( for my Player One Saturn SQR with 1.25x Barlow its 5 pixels), then make the selection a mask.
8) Now a curves adjustment layer can be used to brighten the prominences without affecting Surf.
If you dont have PS, other photo processors (GIMP) have same layer and masking capabilities
I used to take two separate exposures, one normal and one exposed for proms, but realized that a normal exposure still contains enough prom data that that they can be resurrected by using curves. Its been my experience that the limb looks more natural using one exposure than dealing with minor differences that are inherent in two separates.
Fascinating and I’m going to try it. Thanks!
Did you do that on all 3 still images of the Sun of yours on here? The rest are animations, I’m guessing you didn’t do it on there?
If not all 3, can you tell me which of your images on here you did with this technique?
Someone else suggested also shooting at a lower gain. I’m at 75 percent histogram, maybe I should try 70 or even 65.
I definitely used it on 6/3 and 6/6 I can’t recall if I used that on 6/1 but I think so. @BYoesle on cloudy nights suggested to me that two exposures are not necessary.
For the animations I have been doing a similar process on the completed animations, but using the free version of Davici Resolve. It took me a while to figure out how to do it, but it seems to work OK.
I love doing the animations but they take a lot of effort.. setting up the guiding and tweaking the focus every 15m as the temps shoot up. I’m very much a beginner and if you (or anyone) has any suggestions for improvements I would really appreciate it.
As for the gain, I’m uncertain, I’ve been setting it to below 100 or even at 0 for the FD stacks, but raising it over 100 for the animations to keep the exposures below 10ms. For FD images I’m experimenting with using a composite of two frames using the ASI585MM with no Barlow as opposed to one frame with the SQR + 1.25x Barlow. The FDs that I’ve posted here have all been one frame with the SQR + 1.25x
What setup are you using?
Can you post an unprocessed image after stacking so i can check it out?
The double limb you are seeing, will always be seen if the etalon bandpass is not small enought and out of band rejection is not big enought to fully reject the photosphere. This can be seen as a perfectly round limb beneath the chromosphere. Doublestacking or a smaller FWHM filter will fix this, giving you the 3D looking images over the limb. You can check out my images at astronominik.at there are some limb shots with a single and a double stack comparing these should show the difference.
Solartoolbox might be a good option for you. it has a feature to selectifly edit the Proms or surface. This makes it possible to somewhat mitigate the limb effect when processing.
Check this CN post showing the double limb:
https://www.cloudynights.com/forums/topic/696951-what-does-double-limb-look-like/
Great info. Thanks!
I didn’t know about seeing the side of chromosphere through itself in single stack.
At bottom of this post is a JPG save of an unprocessed image TIFF just out of Autostakkert. No imPPG, no nothing.
I have a second stack I will be using, I am trying to master basics single stack first. I have a Lunt 40 in an RAF (with light leak tuning hole coverable, lol)
Mark Johnston aka azastroguy told me yesterday on Facebook that double stacking would help.
His solar shots, like yours, are pretty great, so I bet that’s most of it.
I’ve also been shooting too hot. I shot today at 65 on histo, not 75, after I discovered Highlight Over Exposed toolbar effect in SharpCap.
My gear is Astro-Tech AT130 EDT (Apo Triplet, 130MM, f/7, focal length 910mm), Baader135mm front-mounted full aperture Energy Rejection Filter, DayStar Quark Chromosphere version, Player One Apollo-M MAX camera, (but as of today, cam with Sony IMX174 sensor, Zwo, but also am getting Player One Apollo-M, since I love Player One), Player One Solar Fast Tilter. FlatCap from DayStar, Sky-Watcher EQ6-R Pro. SharpCap Pro, AutoStakkert, imPPG.
These are probably the best shots I’ve done
https://www.astrobin.com/8ldpfv/
Those are single stacked.
These are double stacked, aren’t as good, are from earlier (I’ve only been doing Quark Solar for about 5 weeks.
https://www.astrobin.com/57m8q9/
Thanks!
📷 unprocessedQuarkSingleStack.jpg
First off. Your raw stack looks great for a single stack in my opinion.
It’s really uniform and the contrast is good. With contrast would be even better with two etalons, but for SS its good.
You might find that when you try to use your double stack, that its kind of hard to get a uniform image.
So i recommend you use flats if that is a problem when you introduce the second etalon.
I usually do flats by just defocusing on an aria where there are no spots or filaments in the middle of the sun.
Others doing solar imaging use a thin plastic bag in front of the main optics to take flats.
Just a heads up because i struggled with this for some time when getting my double stack to work.
“I’ve also been shooting too hot. I shot today at 65 on histo, not 75, after I discovered Highlight Over Exposed toolbar effect in SharpCap.“
I disagree. I think this image could be brighter to get the proms farther way from being underexposed. The bright spots(flaring) around the sunspot don’t seem to be overexposed in the .jpeg you sent.
But I’m might have just misunderstood that paragraph.
Now to your original question.
Looking at the Limb of the sun in the image you posted you can see the double Limb effect i described above.
I found it impossible to get a smooth transition when using a single stack on my images which is why i tend to ether stick to just proms with a overexposed disk (giving more dynamic range in the proms) or surface images when using just one etalon.
There might be a trick that helps but in my opinion there is no way to get a good looking image trying to force the proms being bright whilst the surface does not lose details because of the double limp
For example the prom on the right in the .jpeg is dim, when you push it to be as bright as in the first image you posted you will always get a charring transition. I tried to play around with the .jpeg in imppg but the jpeg is just not a great input format.
If you want me to try editing the image you could send me a .tif version via email to astronominik@protonmail.com.
It’s hard to say because taste is different, but you might have overstretched the first image, losing some details on the surface in the right upper corner.
I hope astrobin won’t be mad if i recommend another forum on here, but you might want to check out solarchatforum.com. It’s a really lovely community over there with great imagers that might know some trick to get the look you want.
Sorry if i have overloaded you with information.
Also all of this is just my 2 cents so take it with a grain of salt.
Hope i could help in some way.
You are of to a great start.
Clear skies and loots of Sunspots
Dominik
Michael W. Dean · Jun 8, 2026, 08:07 AM
unprocessedQuarkSingleStack.jpg
LLichter · Jun 9, 2026, 05:49 PM
You might find that when you try to use your double stack, that its kind of hard to get a uniform image.
So i recommend you use flats if that is a problem when you introduce the second etalon.
Thanks!
I do shot Flats, and apply them. I use the Capture / Flats tool in SharpCap Pro. For single, and double etalon.
I tried using a bag early on but it wasn’t great. I’m using a purpose made Flat Cap from DayStar:
https://agenaastro.com/daystar-instruments-flat-cap-imaging-diffuser.html
I don’t have this .ser file, I’ve been deleting them as I go until I get ones worth saving. But will send you one from the next batch. And during next batch, I’ll shoot both single and double etalon, and mark them as such.
I didn’t know about the Double Limb issue and how double stacking solves it, until this thread. It makes sense though! Looking at double stacked images with that in mind I see a lot less of it.
I’ll join that other forum, thank you! I really really doubt this site’s owner here would be upset at someone sharing a useful resource.
Fun double entendre meme I made… 📷 cloudy Nights Newton correct 11.jpg
Glad i could help.
Love the CN burn xD
LLichter · Jun 10, 2026, 10:19 AM
Gald i could help.
Love the CN burn xD
Do you have a link to your solar pics? I thought you had 4 the other night but I only see one (non-solar) image on your page here.
confused.
i havn’t uploaded any of my solar images to astrobin yet. Didn’t get around to it. I will do this in the coming month.
My images and animations in addition to my setups and 3D printed parts for solar can be found on my website here:
when you look at the sessions subpage you can find more images than on the main page including infos on which setup i used.
The setups, exluding my SHG700 and Triband SCT, i use can be found at this link.
There is some info on the website on the processing and imaging workflows i use to.
Feel free to check it out. There are no ads or traking on the website, its just a tool for me to share my images and catalog them. On mobile the subpages are kind of hard to find, there is a hamburger menu in the top left corner.
If you have any questions send me an email to astronominik@protonmail.com or pm on Astrobin
Thanks. Looking at it.
Did you reply here about 10 minutes ago and delete it? I got an alert from you and there was nothing here when I looked.
Hey, since you’re up, can you please send me a DM here? I want to see if I get an alert. I just realized I missed an important notice a few months back, and I think I have it fixed now for alerts.
Thanks.
LLichter · Jun 10, 2026 at 10:19 AM
Glad i could help.
Love the CN burn xD
Just curious why the dislike for CN, I assume it’s for the CN solar obs forum? I’ve been on it for a couple of months. I understand if no one wants to publicly express their opinion and if thats the case please shoot me a PM.
Dan
I don’t mind talking about it as I was banned a number of months ago. CN just isn’t a platform for free, open and frank discussion. If you offend the wrong person, you’re gone. That’s my take…
dan baldwin · Jun 10, 2026, 02:15 PM
LLichter · Jun 10, 2026 at 10:19 AM
Glad i could help.
Love the CN burn xD
Just curious why the dislike for CN, I assume it’s for the CN solar obs forum? I’ve been on it for a couple of months. I understand if no one wants to publicly express their opinion and if thats the case please shoot me a PM.
Dan
Well, that meme I just posted is NOT about the website. It’s about actual nights with clouds.
That site has issues though.
Moderators that over moderate. Even if you give someone BARELY tough love constructive criticism, they act like it’s kindergarten and yell at you for doing it.
Example, I asked a technical question, and a guy with NO experience answered with a wrong answer. I replied on the forum to him “Hey, I’ve done that too, on other forums a long time ago, so I understand, but maybe you shouldn’t do that? Someone else might see it and think it’s right. and that’s good advice in life, not just here.”
I got yelled at by mods for that.
Also they lock posts that bring up real complaints about issues with vendors. Maybe because the vendors advertise there.
Here:
Though similar also happened to me here, but the post just got deleted here. (That and another thing here makes me reluctant to even reply about this here. I’m maybe treading on eggshells with this)
CN let those get posted on for a while and did not delete the thread, so it still shows up in Google searches and AI questions. So that’s good. People need to know things like that. Read both of those threads first post and you’ll see why it’s good info to have as public. Not only did both vendors I was reporting on make a mistake, worse yet, they dealt with it horribly)
CN also has a rule of “No editing a classified ad more than once the same day.” I edited one once at 2 pm on a Monday then the same ad I edited (small edit) at 1 PM on Tuesday.
I got in trouble for that.
But that’s not the same day. If they mean “within 24 hours” they should say it. I told the mod that, and said maybe they should clarify that, and got in trouble for it. Guy was really mad, said “IT’S CLEAR. IT SAYS ‘NO EDITS THE SAME DAY’.”
Awful… sounds like it’s becoming like reddit .
dan baldwin · Jun 11, 2026, 01:24 AM
Awful… sounds like it’s becoming like reddit .
Reddit can be better or worse, since each subreddit has its own janitors I mean mods, who can implement their OWN rules and desires that aren’t in the site rules.
Back to the double limb.
I want to share this post from melix showing how bandpass effects the photosphere shining through the chromosphere, simulated using an SHG, because it’s just awesome.
https://solarchatforum.com/viewtopic.php?p=499840&hilit=Simulating#p499840
LLichter · Jun 11, 2026 at 06:50 AM
Back to the double limb.
I want to share this post from melix showing how bandpass effects the photosphere shining through the chromosphere, simulated using an SHG, because it’s just awesome.
https://solarchatforum.com/viewtopic.php?p=499840&hilit=Simulating#p499840
Wow, Clicking that link lead me down a fascinating rabbit hole!