From: "Tim" <tjp314@pacbell.net>

Date: November 13, 2005 9:33:51 PM MST

To: Astro_IIDC@yahoogroups.com

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

Jim:

My guess would be that it's your red gain more than anything else.  I

think the image scale is fine.  If all the modification you've done to

your camera was to remove the lens and add your adapter, then the IR

cut filter is probably still in place.  It'd be a small square glass

(bluish cast) right over the CCD.

Like Milton suggested, try dropping the red gain until the color seems

to first fade, then turn green or bluish, then back up a bit so that

you get a pale brickish color.  Something that I do at the same time

is watch the color contrast between the surface reddish tones and the

subtle bluish white of the limb clouds and the north polar hood.  When

you've got red and blue balanced well, you won't sense a greenish cast

over the disk (like looking through a dirty fish tank) and the red

doesn't swamp the subtle bluish white of the clouds.

I haven't used it this apparition, but my Celestron (Vixen) 80mm f/11

achromat does a nice job on Mars, though the image is rather small.  I

find that with my refractors - a 6" f/10 Jaegers, the Celestron, and a

Megrez 80 SD, finding critical focus is "aided" by the secondary

color, which is more apparent when imaging than it is visually.  In

focus, the secondary color is at a minimum, but just either side of it

the planet (even Mars) will turn purplish then greenish, as those two

colors get thrown out of focus first, depending on which way you're

going.  

best,

-Tim.

--- In Astro_IIDC@yahoogroups.com, "jimchung2338" <jim_chung@s...> 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.  Is this simply a

function of small 

aperture?  

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

stacking at 

80% confidence level with a Unibrain webcam.  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.

http://groups.yahoo.com/group/Astro_IIDC/files/Planetary/marschung2.jpg