From: Alan Friedman <alan@greatarrow.com>

Date: March 20, 2007 10:38:38 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Saturn March 18th

Hi jim -

Great to see your two images a year apart sitting next to each other in the files area - the learning curve is paying off.

Saturn is a really tough nut to crack - it demands good seeing perhaps more than any other planetary subject. You can get some help in moderate seeing by using the red filtered streams (maybe combined with green) for luminance - the steadiness is always better in red. But the light tradeoff with the red filter means using a much slower shutter, which negates much of the advantage (and of course you don't want to bin your luminance data). With my 10" at about f30 even 66ms at full gain is very dim and noisy - at 133ms the brightness is acceptable but the noise becomes evident quite quickly processing a stack of 200 frames. Really the only way to go is to use unfiltered streams for luminance (or a much smaller image scale) - and this requires 6-7/10 seeing for a good result, I think.

Now the happy news is the Clear Sky Clock forecast for our region tonight!!

best -

Alan

On Mar 19, 2007, at 8:31 PM, jimchung2338 wrote:

Hey everyone,

I've given up on trying to get color data from my Unibrain webcam for imaging Saturn and

turned to a filter wheel with my mono Flea. Much better results in my opinion but still

ascending the imaging learning curve.

http://tech.groups.yahoo.com/group/Astro_IIDC/files/Planetary/saturnmar18b copy.jpg

Jim

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