Hi All, hardly worth posting this after seeing Mike's fantastic effort from this morning, but I guess you got to see mediocre to recognise greatness
I'm confused about the results I'm getting on Jupiter. The great seeing I got on the 18th with the Mewlon 180 didn't really show itself till processing, whearas with the C9.25 this morning I thought conditions were quite good, but just didn't come out "in the wash" Looking critically at the avi's from this morning seeing obviously wasn't as steady as I'd originally thought, but I think I'm getting some jitter from the RA drive as well. I'm still getting Onion Rings with the c9.25 and I'm convinced it's NOT underexposure (I've tried the full range) Focus may be a tad off, but I fiddled with it a lot between the 10 odd avis and it hasn't much changed the result of any so must conclude more seeing....
I'd like to get one morning with the C9.25 when I wasn't battling thin cloud and dew to work out what's going on but I just haven't been able to get it all together yet.
Anyway, below is the best 2 of a very mediocre run.
The detail is actually there, it somehow doesn't just "snap into focus" as your previous images.
I know how you feel. I had the same experiences with Mars; the god of war and I just did not get on. A few kms away from me, you were producing fantastic results whereas I was just getting orange blobs.
It might be worth doing a collimation check just to see if it needs tweaking? The other factor may be your RA jitter. The Tak EM200 just keeps Jupiter in the FOV over a period of up to 2 hours – I fell asleep once on the patio and when I returned, Jupiter had drifted a little but was still towards the edge where I had placed him, to avoid my growing collection of dust bunnies.
Mike – now that you have run one of my avi’s, how does it compare to your tracking dob? Is there much difference in planetary movement in the FOV?
Yes, I'm leaning towards John K's explaination of its the seeing, not underexposure that causes the onion rings. It kind of makes sense: In less than good seeing you can see the planet going in & out of focus, as well as the planet changing it's overall diametre when you study the AVI. If you stack different planetary diametre's you end up with onion rings. Does that make sense?
Thanks Dennis ... now you mention it, in the rush I did skip my usualy collimation step (I always rush when there's cloud about not knowing if I'll even get one avi in).
Quote:
Originally Posted by asimov
Nice Robert!
Yes, I'm leaning towards John K's explaination of its the seeing, not underexposure that causes the onion rings. It kind of makes sense: In less than good seeing you can see the planet going in & out of focus, as well as the planet changing it's overall diametre when you study the AVI. If you stack different planetary diametre's you end up with onion rings. Does that make sense?
Yeh Asi, it does make sense to me, perhaps a combination of the two? I'm going to do some AVIdub work on one of these to try and winnow out badly shape distorted frames and see if that helps.
Not a bad effort Robert, still good detail but it's hard capturing something less than your best after your effort of the 18th.
I'm convinced onion rings come from underexposure - with my Saturn I captured on the 22nd, I did one avi with pretty much no gain, so the white meter was around 30. It was very dim on the screen, could hardly see it.
When I processed it, it came out with onion rings all over it. The rest of the capture parameters were the same (collimation, focus, etc), only the gain and gamma were changed - and onion rings resulted.
Seeing may also be a cause as Asi states above, but I reckon that would only show itself if you stacked those bad frames with the good ones. And with the idea being we reject the bad ones, it shouldn't be a cause.
Robert, if you want to send me an avi of one where you got onion rings, the raw frames might show what the cause is.
You are correct Mike: If you stack the bad with the good. In my mind, registax WILL stack the bad with the good if one is not extremely careful.
I just tried an experiment on my last Saturn AVI...which had the onion ring effect, which was my main reason for using less severe waveletts that what I would normally do.
In registax I used the 128 size alignment box & put it directly on the very limb of the globe of a good frame, I then used optimization @ 90% which gave me 523 frames to stack. No sign of any onion rings.
As to the cause...I wish I knew! I could just about guarantee I was not under exposed. I used 30% gain & 50% gamma with brightness probably 30% An interesting problem!
Mike, maybe it's a case that underexposure contributes to the intensity of onion ringing, but I've got some avi's that I've captured with the light meter in K3CCD reading between 230 and 255 (with some burnout in the white bits) and they Still have the rings. As Asi mentioned I think the problem with Registax quality sorting is it's not based on shape so much as sharpness so you can have sharp but badly distorted frames contributing to the stack and I can well imagine this would setup rings around the edge. When my LXD75 is not well balanced I also get a jittery image which might also be a factor. Only way to really test this is of course going through these avi's meticulously culling the out of shape ones and then retry.... need a spare couple of hours
he-he...I've been working on this onion ring problem all day.
Heres my findings so far: Ok, I have an AVI of saturn with onion rings 360 deg on saturns globe. As I mentioned earlier, I put the 128 alignment box on the limb (left side) optimized @ 90% & stacked.
Upon closer inspection I stand corrected...there is onion rings, but not on the left side, there on the right! I then try the same thing, only on the right limb this time, & guess what? Onion rings on the left!! None on the right limb.
My next thing to try is using alignment box size 256 & putting the cross hairs on the right limb (I'm out of ideas on where to put the cross hairs) but still managing to get the whole planet including rings in the box. Geez.
My findings after doing that: Onion rings still present, no where as severe. Also after splitting the image, onion rings are only present in the blue channel.
My findings after doing that: Onion rings still present, no where as severe. Also after splitting the image, onion rings are only present in the blue channel.
See test image. 101 frames.
John, you are one helluva dedicated guy - well done for a marathon investigation and processing effort into the intrinsic nature of onion rings.
Great stuff Asi, I'll have to try playing around with the alignment box size and placement and see what happens. Should start a "We Hate Onion Rings" thread so we can pool our efforts... you want to do the honours Asi since you've done the hard yards so far?
Looking critically at the avi's from this morning seeing obviously wasn't as steady as I'd originally thought, but I think I'm getting some jitter from the RA drive as well. I'm still getting Onion Rings with the c9.25 and I'm convinced it's NOT underexposure (I've tried the full range) Focus may be a tad off, but I fiddled with it a lot between the 10 odd avis and it hasn't much changed the result of any so must conclude more seeing.... 
no where as severe. Also after splitting the image, onion rings are only present in the blue channel.
