From: Phil Houston <pkh111@knology.net>

Date: April 13, 2008 7:55:24 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Lines of Saturn

Hi Alan,

I have been examining the images you posted showing the banding, nice image by the way, and noticed that those lines are vertical rather than angled. Could it caused by the same reason?   I'll buy the idea of aligning on the noise and possibly enhancing the noise.  Looking at videos taken with longer shutter speeds, the banding was absent.  I will try the gaussian blur option and lower the tolerance.  Thanks for the hint.

Since this problem seemed to be rather random,  I never looked into it to check the shutter speeds and noise of the video.  Going back a few imaging sessions I will try to identify any common factors.  If I find any I'll report back.

Thanks again,

Phil

On Apr 13, 2008, at 9:26 PM, Alan Friedman wrote:

Hi Phil,

That is a nasty example of a common problem that results from stacking dim and noisy frames (pretty much the norm for saturn data shot with a monochrome camera and color filters). I've uploaded a couple of stacks from a recent saturn session - about 280 frames were averaged. The stacks were processed in Astro IIDC and then quickly opened in Photoshop to apply an auto levels adjustment. The banding can be seen, though not as serious, and you can see that it is subdued further by using a longer shutter to produce a higher S/N sample in the individual frames. Milton can probably speak with more knowledge on this, but I assume that the stacking is picking up the linearity from the noise pattern in the image.

Are you using the gaussian blur option for frame selection and alignment - and also using a low tolerance for pixel matching? I find both settings are very helpful when the data is noisy and the light levels low.

Hope that you can pull some good results from this session - it looks like the seeing was good.

best regards,Alan