Saturn with ring artifacts question

[stardust steve (Steve)]

Hi.I had another go at Saturn last night in much better conditions. Glad i did as the result is a marked improvement on previous efforts.
However, i noticed i am getting some "ringing" artifacts around the planet and i'm not sure where the planet's rings start
I took about 4 AVI's, and discovered this in the last 3 times i went to process the AVI's.
The first AVI i did did not appear to have the ringing present.
Just wondering if this is normal and people process it out, or maybe moisture in atmosphere, or colimination need to be done?
Here are the stats..
1st pic processed image
2nd pic showing the ringing more (straight out of AS!2 and wavelets stretched to the rhs in Registax6)
2872 frames original avi ( don't know what was stacked in the end)
ASI120MM CCD
SW 8" f5 Newt
(2) 2x barlows giving me a focal length of 4000mm.
Neq6 PRO.
AVI processed in AS!2
Wavelets in R6

Thanks.
Steve.

[Shiraz (Ray)]

pretty good result Steve.

best guess is that the effect is due to seeing jitter - this is often caused by the jetstream. You could try:
- Stack a lot fewer frames to see if that helps by getting rid of frames with bad jitter artefacts.
- Set the minimum brightness threshold (min bright) to zero to ensure that the faint ring edges do not get lost on poorer quality frames.
- Try larger align point boxes and fewer align points
- use a bit less sharpening in R6

for interest, how many stack points did you use?

otherwise, you will need to find a night with reduced jetstream or you could maybe try a higher framerate next time you are imaging, to try to freeze the worst of the seeing - what framerate did you use for these?

[stardust steve (Steve)]

Originally Posted by Shiraz

good result Steve.

that sort of effect is generally due to seeing jitter - due often to the jetstream. try setting the quality level higher so that you stack a lot fewer frames to see if that helps by getting rid of frames with bad jitter artefacts. Also set the minimum brightness threshold to zero to ensure that the faint ring edges do not drop out on poorer quality frames. How many stack points did you use?

otherwise, you could try a higher framerate next time you are imaging to try to freeze the seeing - what framerate did you use for these?

Thanks for the reply Ray
I used 3 align points. There was 2872 frames to start with and i did not change the setting in AS!2 that says use 100 or 50% of frames (they were both green)
From memory i used 14.7 FPS. I was getting more but then changed the EXP i think it was which dropped the frame rate.
I did have the brightness up a bit.
I'm sure my settings were Gamma-24, Gain 70, brightness 7 ( much the same as Alan Gould's settings from his Saturn he posted in Solar System thread) i think i even used .011 exposure.
Thanks for your tips, they have given me something to try asap. It's a bit exciting getting some better results.
I'm hoping to get rid of that annoying black ring just inside the planet's surface.

[asimov (John)]

Looks to me like a gamma problem.

[Shiraz (Ray)]

Originally Posted by asimov

Looks to me like a gamma problem.

yep, don't know what gamma the ASI should have, but would start at 100 - maybe someone who has used the camera can help?

making sure that the minbright is set to zero will possibly help with the data you have. suggest say 10 stackpoints with stack boxes of maybe 60. put them where the image changes - eg the ansae, the junctions between ring and disk etc. click on frame percentage to stack so that a tick shows alongside and set it to maybe 25%.

[stardust steve (Steve)]

Originally Posted by asimov

Looks to me like a gamma problem.

Originally Posted by Shiraz

yep, don't know what gamma the ASI should have, but would start at 100 - maybe someone who has used the camera can help?

making sure that the minbright is set to zero will possibly help with the data you have. suggest say 10 stackpoints with stack boxes of maybe 60. put them where the image changes - eg the ansae, the junctions between ring and disk etc. click on frame percentage to stack so that a tick shows alongside and set it to maybe 25%.

Thanks for the suggestions John and Ray. I will try all of the above and see how i get on.

[EricB (Eric)]

Hi Steve,

I used to havea similar issue with Jupiter until I set the gamma to around 50. That made a difference.

Cheers,

Eric

[asimov (John)]

50 is apparently linear, or default in this camera from what I read.

[stardust steve (Steve)]

Originally Posted by EricB

Hi Steve,

I used to havea similar issue with Jupiter until I set the gamma to around 50. That made a difference.

Cheers,

Eric

Thanks for the tip Eric

Originally Posted by asimov

50 is apparently linear, or default in this camera from what I read.

Cool. Cheers guys, i knew i get some help here, top stuff. I will be trying it out tonight with some luck, high level cloud at present, hope it clears for tonight