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Kieron

Help with Jupiter image, please?

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Hi Folks,

I took some images on 25th (already posted elsewhere) but they are marred by a ringing effect that I described previously as "onion ringing" but in retrospect that is not quite what I meant. As you can see from the image below (contrast and brightness enhanced) there is a bright ring that is off-set to the right of the disk, with a corresponding dark ring on the disk itself.

The channels were captured with a DMK mono firewire camera at 60 fps, 1/60th second, maximum gain, minimum gamma, and processed in Registax. The artefact is not so obvious on the images captured at 30 fps, 1/38th second.

Can anyone tell me what causes this? Some sort of reflection within the imaging train, perhaps? Or is it a processing artefact (stacking, wavelets etc) in which case I have posted in the wrong section :)

Regards, Kieron

post-16312-133877387871_thumb.jpg

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I think I have gone some way to solving this, by searching the TIS forum. A recent post described the same problem and it seems to be linked to the use of 60 fps, as I suspected. Unfortunately TIS were unable to explain why it should happen. D'oh!

Oh well, I will just have to stick to 30 fps, which is a shame.

Regards, Kieron

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Hi Mark,

I followed the link and found some tips on dealing with the "onion-ring" effect, but as I said this is something different - more like ghosting. Or have I missed what you were pointing me at?

Regards, Kieron

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Kieron, what that looks like is a misaligned frame or one that contains a severely distorted image. I haven't played with avi stacking software in a while, especially Registax, so I'm rusty at this. But somewhere in the alignment dialogue, where you select the frames after initial alignment, you can eliminate the ones that are misaligned or distorted. That may solve your issue.

Daniel

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Hi Daniel,

I appreciate your suggestion but I must disagree, as the same artefact can be seen on the individual frames.

Best wishes, Kieron

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Ahh, I see. Is it on all the frames or just a few? If it's just a few of the frames you can remove them from the stacking list. If it's on every frame, I'd talk to the manufacturer. :)

Daniel

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Hi Kieron

I occasionally have had this problem.

Pesonally i have put it down to atmosphere conditions on the night

rather than a camera problem.

I use a mono DMK 21 with RGB filters.

ED

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Thanks for all your comments and suggestions. On balance I think this has more to do with the 60 fps frame rate than anything else - when i get a chance I will do some experiments and post the results here.

Best wishes, Kieron

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Hi Kieron - is it a big file? Can you send me a copy and I'll have a play for you.

Arthur

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OK Arthur, thanks. I'll send you the original RGB stack before further processing/enhancement.

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Arthur,

The AVI for each channel is 343 MB, zipped to 158 MB.

"Captain, she's going to blow"

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Kieron.

You have answered your own question I think, try knocking the frame rate down to 15fps and make sure your histogram is about ¾ the way up, try and keep the gain low.

Trev.

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I made some comments in the other section Kieron and I am no wiser than anyone else here but I really don't think the higher framerates are the culprit per se.....which might sound a little silly seeing they manifest themselves on the 60fps only.....but by this I mean that you could easily (imho) shoot on another occassion at 60fps and get none of the problematic....!

In my brief(ish) endeavours with planetary (which has become obsessional!!!:):):eek:) I am ceasing to be amazed at the "pecadillos" processing throws up.....as I previously stated, sometimes R5 will resolve a processing that R4 won't and vice-versa with no real rhyme or reason.....but in this instance if looking at the framelist reveals these "artefacts" on each frame then it would seem to suggest the capture control settings or "atmospherics/optics" as the root cause.....so perhaps the combination of gain (and gamma!) to get the exposure necessary at 60fps is the culprit!!!

Though this doesn't seem to be a relative of "onion rings" in my (extensive) reading about that problem I have never found any conclusively explicit rationales for said and concluded that in that situation it is a combination of settings that create said - and not, as some would believe, merely an abundance of gamma.....some fine planetary imagers utilise 50-55% gamma - gamma shifting the entire histogram one way or the other and gain extending it.....hence my thought that it is the specific combinations thereof as above (possibly) also taking into account framerate and exposure settings also impacting upon the histogram etc as part of the total mix.....

I checked out "Dave's Astronomy" link in this thread and without in any way detracting from what I presume are excellent images and info I did beg to differ on a couple of quick things I read therein.....some of the finest Jupiter imagers use 150second (2.5 minute) exposures to create the most superbly detailed images available as opposed to Dave's "less than 2 mins" and also re his comments on Saturn and the lack of belt details etc with elongated exposure times.....some of my own (poor colour renditions) of Saturn here on S/GL with a humble 6" achro and toucam reveal cloud details and storms clearly by also limiting the exposure time to 150 seconds.....

This is only to say that there are many variant opinions on much of planetary imaging's techniques and problem resolution, and one needs to sort through the manifold factors extensively before making specific tenets....!:rolleyes::icon_salut::)

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Hmm - it took longer to say it, but that's what I said... Registax can be a bit of a [removed word] sometimes.

Arthur

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Hmm - it took longer to say it, but that's what I said... Registax can be a bit of a [removed word] sometimes.

Arthur

.....well, my "tome":laugh::):eek: isn't merely "fingering" Registax and its permutations.....also pointing out that specific combinations of (often) a raft of factors (capture setting combinations, optical and atmospherics etc) can come into play; and that it can be quite erroneous to subscribe to some single factor as the root cause.....:)

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This is only to say that there are many variant opinions on much of planetary imaging's techniques and problem resolution, and one needs to sort through the manifold factors extensively before making specific tenets....!:):icon_salut::)

Thanks for your interest in this. Like you, I spent a long time trying to do planetary imaging with a six inch achromat and ToUcam. I learnt a lot about processing! Although its a lot easier with my current set-up I still have a lot to learn.

Regards, Kieron

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