From: Alan Friedman <alan@greatarrow.com>

Date: March 26, 2007 10:44:17 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Saturn from the first hours of spring

Thanks very much Ray!

best regards -

Alan

On Mar 26, 2007, at 5:30 AM, Ray Byrne wrote:

Hi Alan,

This is the best I've seen this apparition (I'm on Cloudynights Planetary imaging forum so see quite a lot of stuff and Damian Peach has me on his mailing list so I see his stuff too) thanks for sharing. Also a big thanks for explaining your method. Actually on a thread in the aforementioned, one chap said "we don't use Macs here we use PCs". I put him right about the use of Macs in planetary imaging by pointing him to your site, he later said "well it doesn't matter what platform you use it's the results that count" which actually is fair comment.

Clear skies and good seeing to you!

On 25 Mar 2007, at 19:43, Alan Friedman wrote:

Hi all -

Here's a first processing of Saturn captured with the 10" mak on March 20th in a nice little

pocket of steady air that arrived just after the vernal equinox. (Follow the thumbnail link to

the picture from the "Latest Images" section of my website) -

http://www.avertedimagination.com/latest_1.htm

I found (with help from Milton!) four moons lurking nearby, so I stretched the image

enough to bring them out and included them in this picture.

This image was prepared using the image processing component of Astro IIDC. The data

used was captured through RGB filters - 3 streams each of R and G, 2 streams of B. About

350 frames of 1200 were stacked from each stream. Each stack was aligned four times,

two for the ring ansae and two covering the edge of saturn's disk. Final assembly of the

picture is done in Adobe Photoshop CS2. This was my first real effort at developing a post

processing workflow in Astro IIDC - it worked beautifully on this data and saved a BIG pile

of time over my usual hand selection routine.

Usually I glean my luminance (detail) information for Saturn from video streams shot

without a filter. At the focal length I prefer (8-11 meters) the RGB filters absorb so much

light that a slow shutter (66ms or even longer) is needed. These streams tend to be either

grainy and dim, or very soft if given an adequate exposure. This night the seeing was

good enough that the data was sharp even with exposures above 1/10 of a second. I was

able to stack a third of the RGB frames for an image that was quite smooth and didn't

require heavy processing. I sharpened the final image by making a luminance layer from

just the red and green data and added this to the color composite - a technique I have

used for a couple of years on (much brighter) Jupiter. I would guess the seeing approached

8/10 at times - a hint of the Encke division was visible in the blue filtered data - quite

unusual from my location.

I still have a pile of unfiltered data to go through and perhaps add. I don't think it will

show any additional detail (there were no spots or storms that I could detect) but it will

probably make the final picture a little smoother and prettier.

Hope you enjoy this first working version -

Alan

ATB

Ray Byrne

in4media | graphic and website DESIGN

T: 01793 435704

W: http://www.in4media.co.uk

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