Them Damn Onion Rings!

[StuW]

Here's one from the 23rd with the ZW Optical ASI120MC OSC camera and a 200P-DS. Can't seem to get rid of those damn onion rings.

I'll be posting a raw AVI somewhere later to see if it's just my processing..

[Keiran]

Looks like a nice image of jup to me, although i am impressed to how you have travelled forward in time to take this Youve put 23rd dec on your site

[sologuitarist61]

Looks a good image to me

[StuW]

Says 23rd Nov to me??

Looks like a nice image of jup to me, although i am impressed to how you have travelled forward in time to take this Youve put 23rd dec on your site

Here's the avi. just over 300mb D/L, but unpacks to 3gb

http://dl.dropbox.com/u/13321962/Capture%2023_11_2012%2023_57_38.zip

[bus_ter]

more gain when capturing? Or increase the colour bit depth if you have control over it.

There was a good post about what causes the effect, and how to prevent it.. can't find it though!

EDIT: Some info to read here:

[StuW]

Thanks Bus_ter, I'll have a read..

[JamesF]

I've always associated onion rings with insufficient gain. What capture application are you using?

James

[StuW]

Sharpcap, but the camera is very new so not a lot of info on best methods yet

[BuzzBomb]

It's a good 'un. Got the detail and focus there. Not seeing the onion rings on my phone so maybe not so bad.

Lots of experimentation needed with planetary imaging to get the best result.

Sent from my GT-I9001 using Tapatalk 2

[Uplooker]

Hi Stu,

Thats a good image. Considerably better than my effort. I was trying to image at the same time as you. I know this as when I was waiting for the clouds to clear I had a quick surf of the forum and saw you post of images you had taken of M27 and some others. I really struggled to get the focus right and the seeing seemed atrocious. Obviously not that bad as I am only a couple of miles down the road from you - as the crow flies.

Ian

[Kevstew]

jupstuw.tifi often suffer from the onion ring effect too and i dont know the answer to the problem. ive just been experimenting with different capture and processing settings. i had a quick go at processing your avi using as!2 registax6 and gimp the onion rings are still there but theres a slight impovement.

[Kevstew]

jpeg verson

[StuW]

Thanks for trying Kevstew, at least I can stop thinking it's my processing causing it and try looking at my capture technique. You've managed to get a bit more detail than I did as well!

[bus_ter]

I downloaded your video. Amazing how over 3GB compresses to 130MB! If only there was some sort of lossless compression like that in camera, the frame rate jump would be massive.

The video quality is good, but it's very small. See if you can get a good quality barlow in the mix.

Anyway here's my take on your video..

[Space Cowboy]

I've recently seen some great images with this camera so there is massive potential here. As has been said it looks like gain needs to be higher judging by the faintness of the moon. Sometimes gamma can need either lowering or raising, I know with my dfk rings appear if gamma is just below the default setting but not if its much lower. Experimentation is the key.

[StuW]

bus_ter the disk size is really too small? That is with a 2x ED Barlow and 120mm of extension tubes, I do plan on getting a 3x or higher sometime soon so hopefully that will help.

Space Cowboy The camera is fantastic my sharpcap settings were

[ASI120MC Camera (ZWO Design)]

Frame Divisor=1

Resolution=640x480

Frame Rate (fps)=Maximum

Colour Space / Compression=RGB24

Pan=-320

Tilt=-223

Exposure (s)=0.01561

Gamma=1

WhiteBalance=5000

Gain=26

So maybe more gain as you say, and i'll play with my gamma aswell.

[michael.h.f.wilkinson]

The image is pretty good, I would say. As I have said elsewhere, I set gain and other exposure parameters manually (each time, as transparency varies), in such a way that the histograms of the R,G, and B channels use almost the full range of the ADC, without clipping on either end (i.e. bins 0 and 255 of each histogram must remain empty). This ensures minimization of discretization error, and reduced onion rings. Even if the colour balance of the AVI seem off, you can correct that later.

[StuW]

Thanks or the tips Michael. Hope it's not too long until I can give them a test.

[Keiran]

Says 23rd Nov to me??

http://stargazerslou...07_513_8743.jpg

[StuW]

Ahhh the description, I thought you meant further down lol.. Thanks, I've fixed it now.

[Baz Pearce]

I've always associated onion rings with insufficient gain. What capture application are you using?

James

Don't think i thanked you for that tip James. So i'll do so now. Cheers, and thank you. It certainly worked for me. Since then i have always kept my gain setting at least 75% on the slider and i adjust the shutter to compensate for the extra brightness. I've not been seeing any rings since.

Baz.