NEW Image added: Stacked image worst than single frames???

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NEW Image added: Stacked image worst than single frames???

Post by H-Alpha »

Hi all,

Now that there is not a lot of solar activity, I thought to make some improvement tests...

The answer to the question of the title is obviously that this could not happen, since we all apply lucky imaging and stacking in order to get the best of all our frames into one single image. Nevertheless, after my first steps in solar photography in the beginning of this year I have been suspecting that my stacking results with AutoStakkert!3 might not be as good as I was expecting them to be. My doubt became even bigger when Alexandra with so many years of experience had also doubts about her stacking results a couple of months ago.

Therefore, I visually compared my stacked image, which was the result of 100 frames (the best out of 2500) with two single frames of the same video capture; the best (number 1) and the worst (number 100) according to AutoStakkert!3 (that allows for saving whichever single frame of the capture).

Here follow the astonishing results:
Stacking comparison with single frames.jpg
Stacking comparison with single frames.jpg (3.8 MiB) Viewed 127 times
I suppose that you will all agree that the stacked image is blurred in comparison to single frames, which show much more details than the stacked image. If you enlarge the composite image, you will clearly see WL granulation cells and there borders that are not visible in the stacked image.

Is this something "normal" for all of you and stacking in general, or am I doing a stupid terrible mistake with AutoStakkert!3 for months now? AutoStakker!3 is quite simple with not many menus. I really cannot figure out where I am wrong in using it.

To make the test more useful and conclusive, I would like to kindly ask any of you who have the time and will to try to stack the video of my 100 frames, so that we can see if better results can arise. The video (~200 Mb) can be downloaded from Flickr (you can open it in a New Tab and then download it). For some reason it appears black in Flickr, but when downloaded it plays fine:

ImageSun WL_17_44_53 STACKING TEST - 100 frames by H- Alpha, on Flickr

For some reason it appears black in Flickr, but when dowloaded it plays fine.

Just a last detail. In the composite image above, I have increased the contrast and sharpness in photoshop with the very same action in all three photos, in order to make the comparison clearer. I have included below the same composite image of the originals, so that they can be compared with any stacked image you may be willing to create for comparisons.
Stacking comparison with single frames - Originals.jpg
Stacking comparison with single frames - Originals.jpg (2.16 MiB) Viewed 127 times
Thanks a lot in advance for any help you may provide!

Best wishes,
Alexandros
Last edited by H-Alpha on Thu Sep 16, 2021 7:54 pm, edited 1 time in total.


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Re: Stacked image worst than single frames???

Post by Montana »

Alexandros, welcome home :hamster: I hope you had a good time at sea :)

The stacked image will always come out blurred, have you applied deconvolution or sharpening in ImPPG?

My problem is that even after sharpening it is not as clear as a single image. I came to the conclusion that you need absolutely perfect seeing for that 100 images to get good stacking.

Alexandra


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Re: Stacked image worst than single frames???

Post by H-Alpha »

Thanks a lot Alexandra,

Yes, the expedition was very successful but exhausting as well. Both climate change and ...getting one year older make it challenging every year. ;-)

Yes I apply both deconvolution and unsharp in ImPPG, which improve significantly the stacked image, but creates lots of noise in the single frames. Is this the only benefit of stacking? I hope not, so that improvement is possible.

Concluding, I understand from your message, that a blurred stacked image is normal... (unless we have perfect seeing). Hope other people here will try to stack the video that I have uploaded, to show that stacking can give better results.

Best wishes,
Alexandros


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Re: Stacked image worst than single frames???

Post by Montana »

I'm glad you had a good time :) but I can imagine it was tough!

The stacked image is the only one you can sharpen. It will always be blurred out of ASK3, you then apply sharpening. The single frame images you cannot sharpen, they are as the camera captures (flat image). If you tried to sharpen them all you would achieve is noise. The point of stacking is an overall clear image. If you look at each frame of your lucky imaging some areas will be clear and other areas blurred (atmospheric ripples). ASK3 takes each portion of the 100 images and pieces together only the clearest areas to give an overall clean and clear image. Because the images are stacked they will need to be deconvolved to show the original detail again.

Therefore, your stacked image should show the same level of detail (after deconvolution) of the clearest portions of each of your single images, but clear over the whole image.

I hope this makes sense. I was finding my stacked and deconvolved images were not anywhere near as clear as all the clear portions on a single image.

Alexandra


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Re: Stacked image worst than single frames???

Post by EGRAY_OBSERVATORY »

Hi Alexandros,
I also often find much the same as you in either Ha and Ha-Ds, Cal-K, Sodium and WL, whilst using SharpCap, AS-2 or AS-3 and I was starting to do some comparisons as you have very well done.

In fact the last two or three sessions (or more) have resulted in me using single-frame captures for posting, from my two Lunt 60mm's and the new Skywatcher 'ESPRIT' 80ED for the WL and Sodium.

I actually posted a comparison result here, to show that even IMPPG does not always seem to resolve some issues either, but then I need more time and work to find the solution.

I feel that if the seeing is perfect and the mount is tracking very well, then with fast or very fast captures times (especially with the Sodium), then the single frame capture is sufficient to capture all the detail necessary.

But (and there has to be a but), once one starts using Barlows of any sort, then of course the tracking and the weather conditions has to be even more perfect - which is not always achieved, otherwise not only are you magnifying the part of the Sun, but magnifying the inaccuracy of the tracking mount and weather... Similar to using a low and then high-powered pair of binoculars on the same target by free-hand...

In my opinion, stacking is for images where those conditions are not absolutely perfect (as described here) as:- for better alignment of the moving image due to those less than perfect conditions where otherwise a single high-speed capture could well suffice.

Also just to mention, that I see that some of your images are in excess of the 2-Mbytes as requested by :-
viewtopic.php?f=4&t=31518
So to reduce those posted directly on SolarChat and save the SolarChat server - the necessary space to save paying- advertisements from clogging-up our screens and also for far-quicker viewing of such images by us.

Reducing the JPEG size slightly, will not reduce the image quality of any part of Solar-imaging, by any significant amount...

I trust this will help you a little..

Best Wishes
Terry


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Re: Stacked image worst than single frames???

Post by H-Alpha »

Thanks a lot Alexandra for the further details and Terry for your precious remarks that describe very well the results of my (limited) experience!

Terry, I had in mind Mark's posting regarding the size of images and remembered well that he mentioned that photos of a couple of Mbs are acceptable and this should be the limit for solarchat not to be overcharged. Therefore, I considered that my photos of 2.16 and 3.8 Mbs were fine to upload. However, thanks to your message I went back to the post of Mark and saw that just below his post you put the upper limit to 2 Mb, so thanks for your reminder! ;-)

Best wishes,
Alexandros


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Re: Stacked image worst than single frames???

Post by marktownley »

Hi Alexandros.

You're stacking 100 out of 2500 frames, how many 2500 frame captures are you doing? What setup / scope / camera is this with?

Mark


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NEW Image added Re: Stacked image worst than single frames???

Post by H-Alpha »

marktownley wrote: Thu Sep 16, 2021 7:13 pm Hi Alexandros.

You're stacking 100 out of 2500 frames, how many 2500 frame captures are you doing? What setup / scope / camera is this with?

Mark
Hi Mark.

Sorry I did not mention the setup.

Lunt 130MT+1800BF, ZWO ASI290MM, Baader Solar Prism, ZEISS Abbe Barlow 1.6x, UV filter

I make a few tens of 2500 frame captures (some 30 that day) during the best moments of seeing: sometimes when I visually have the best seeing conditions and others when the SSM indicates that I have the lower value.

By the way, today I had the best definition of WL granules I ever had since the beginning of the year, when I started solar imaging. The funny thing is that today my SSM values were significantly worst than yesterday (the Jetstrean forecast as well...). However, what I could see in my screen was much better than I have ever seen, and this is what counts at the end.

Here are today's results. Please open in a New Tab and enlarge to see the granulation cells:
Image2021-9-16, sun wl_17_48_13_uv composite by H- Alpha, on Flickr

and cropped to make the granulation cells better visible:
sun wl_17_48_13_uv dark B&W sharp cropped.jpg
sun wl_17_48_13_uv dark B&W sharp cropped.jpg (550.6 KiB) Viewed 43 times
and here is a part of the video capture (cropped and shorter) that resulted in the above WL photo (it plays correctly only if downloaded; don't know how to make it play directly here):
Image2021-9-16, Sun WL_17_48_13_UV cropped by H- Alpha, on Flickr

Despite all this, my image is still light years away from the definition of images that people often upload here with much larger scopes or XBarlows, and I still wonder what could be their seeing (apart their experience and techniques) to achieve such wonderful results. An example is the recent amazing WL photos by Alessandro:
download/file.php?id=59252

Mark, do you think that with a larger scope today I could image the cells larger and more blurred or larger and clearer?

I think I will start to move in other places to test local seeings... (although this is hard to do and costly as well). In the meanwhile, I will ask people from here who achieve miracles to kindly share some short RAW Video captures in order to see what they see on their screens when they are imaging...

Best wishes,
Alexandros


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Re: NEW Image added: Stacked image worst than single frames???

Post by marktownley »

Very nice, are todays single images or stacked?


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Re: NEW Image added: Stacked image worst than single frames???

Post by H-Alpha »

marktownley wrote: Thu Sep 16, 2021 9:39 pm Very nice, are todays single images or stacked?
Thanks Mark. Today's are stacked images. Exactly the same stacking and processing (ImPPG) procedures as the previous day. Just better actual seeing! :-)

I think that as Terry wrote, better seeing allows for much better stacking, which comes much closer to what we see in single frames.

All the best,
Alexandros


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