From: Milton Aupperle <milton@outcastsoft.com>

Date: November 13, 2005 12:18:03 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Mars image Nov 13/05 - advice?

Hi Jim;

On 13-Nov-05, at 12:10 AM, jimchung2338 wrote:

Hi all,

This is probably my best attempt at imaging Mars through my 17 year old TV 76mm

Oracle refractor - a triplet apochromatic. I simply cannot get any more detail and I

think the focus is optimized as is the brightness.

Not to criticize, but it looks like you either your not using an InfraRed Filter or have too much red gain.

If you don't have an IR Cut filter, especially with objects that are illuminated by the sun, you tend to get washed out colors AND a marked increase in red intensity. It's very tough to re-balance the colors under this situation, especially when there is no blue.

If you are using an IR Cut filter, then try reducing the Red gain quite a bit. With the Moon being out, I normally use it for focus and also a sanity check of my color balance to see if it's "reasonable" or not.

To get a feel for the color balance, I use Apple's "DigitalColor Meter" (it's in /Applications/Utilities/") and it shows the bright half of your Mars image is about 70% red, 30% Green and 0% Blue. So you have a complete absence of blue in the image and most of the "dark patches" are about equal amounts of RGB. I did a quick check on several other peoples Mars images and came up with an average of 40% Red (range 30 to 50%), 32% Green ( range 29 to 34%) and 27% Blue ( range 19 to 40%).

Is this simply a function of small

aperture?

Largely yes as aperture is tied to feature resolution, but it also depends on seeing too (see next paragraph). I use a 127 mm aperture scope and with barlows + projection achieve a 4100 mm focal length and I'm only getting mars that is 75 pixels across (your Mars about 40 pixels across). People like Allan and Tim are using 200 to 300 mm aperture scopes and getting images in 150 to 200 pixels in size. The other issue is that the larger the aperture, the more light it gathers and the shorter the exposure time you can use. With short exposure times you can reduce the affect turbulence has on the image. If I had a 10" scope with the Flea Color camera, I could run at 60 fps and exposure of probably 10 milliseconds per frame and that would reduce the turbulence affect even more.

Again taken through a 5x Powermate at approx f37, 120 ms exposure stacking at

80% confidence level with a Unibrain webcam.

How good was your seeing when you took the images? It was clear over Calgary on Friday and Saturday night. But Friday the Jet Stream was right over top of us and and no matter what I did, Mars was a fuzzy ball with the upper half red and the lower half a bit darker, similar to what your getting. On Saturday (before the clouds rolled in completely at midnight) the jet stream was way south of me and I could pick up Olympus Mons repeatedly in all my stacked images over 2 hours. Nothing changed but turbulence.

BTW there was some discussion than

the Unibrain has a nonstandard thread/size and I know for that reason that Mogg

won't make an adaptor for it. I found some plastic electrical conduit threaded pieces

that you screw directly into the webcam case (after removing lens assembly) and

some light sanding brings it 1.25 " size.

Very cool and thanks for the tip. I built my own adapter using plastic plumbing parts and epoxy - but a non permanent screw in solution would be much better. You wouldn't happen to remember where you bought the electrical conduit parts and any details (i.e. part numbers, dimensions etc.) on them, would you?

Hope That Helps..

Milton J. Aupperle

President

ASC - Aupperle Services and Contracting

Mac Software (Drivers, Components and Application) Specialist

#1005 - 815 14th Avenue. S.W.

Calgary Alberta Canada T2R0N5

1-(403)-229-9456

milton@outcastsoft.com