From: Alan Friedman <alan@greatarrow.com>

Date: March 26, 2007 10:42:20 AM MDT

To: Astro_IIDC@yahoogroups.com

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

Hi Phil -

Thanks very much for your note and thoughts.

The zen of astronomy in a place like Buffalo resides in the long stretches between clear skies and the even longer stretches between good seeing. There is lots of time to explore your data. The image is mostly done in that I don't think the unfiltered data will add much if any additional detail. I did get to spend some time with the image processing possibilities of Astro IIDC working on this and I found a nice work flow that is much more automated than my usual time consuming hand selection process. It seemed to work very accurately with data of this quality. I collected about 28,000 frames in 23 streams during the periods of good seeing last week. I was able to process it all while watching (with one eye) Casino Royale on TV with my family (a movie that looks just as good with one eye as two!.) My images are usually made from a small number of frames compared to many I see done in Registax with thousands of frames. I'm curious to see if improvements can be seen with the addition of more signal. I expect it will not change it very much.

best wishes -

Alan

On Mar 26, 2007, at 1:04 AM, Phil Houston wrote:

Alan,

If I were you, I would seriously consider saving time and just call your latest masterpiece finished. The image you have assembled shows much more than good equipment, good seeing, or good luck, it demonstrates an artistic skill that I find rare to this type of imaging. Very pleasing to the eye.

Phil

On Mar 25, 2007, at 2:43 PM, 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

__._,_.___

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