From: "Michael T Snider" <snidermt@aol.com>

Date: October 5, 2005 12:35:51 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re:  Mars on 2 October 2005 and observations on atmospheric dispersion (long) / 

Hi All,

Following my last post, in a direct e-mail to me Bob Young astutely

observed that  "It looks to me that the area above Syrtis Major, in 

your pix, about Aeria, is pretty bright.  You ought to try to image

it with a red filter, like a Wratten 25, and also a blue filter, there

maybe dust there.  It would be bright in both colors."

No need to wait and reimage on another night with a Wratten 25A

red filter and a Wratten 47 blue filter. All the needed data is

already on the color QuickTime clips that I took in raw format with 

the Sony XCR-X710 CR camera.  The blue and red panes of the 

RCB picture are each sampled with 25% of the pixels on the chip 

which are covered with the appropriate blue and red filters. The 

other 50% of the pixels sample through green filters similar to a 

Wratten 58. As the optical image dances on the plane of the CCD

over successive frames, pixels in the image not covered by the the 

other filters receive appropriate data to fill in the image,

To illustrate this, the red, green and blue panes of the images from

the 2001 frame stacks on 2005 10 02 with South on bottom were 

extracted with PhotoShop CS and Grab. These along with the IR 

and color images are shown in a summary collage with South 

toward the bottom.

http://homepage.mac.com/snidermt3zp/PhotoAlbum29.html

To better look for evidence of a dust storm in Aeria, I selected the

sharpest 506 of the 2001 frames by Fourier analysis and 

reconstructed the Mars pictures correcting to "different color 

temperatures". These were rotated to so South is on top.

The "best" color image was labeled to identify the structures. I can

just make out the crater Herschel (198 miles in diameter, 0.85 

arc.sec on this date).

This color image was dissociated into red, green and blue panes and 

displayed with the color and IR images as a summary collage.

Aeria appears bright in the red, green and blue panes and thus is

probably not a dust cloud. Perhaps this is an atmospheric limb effect

in the Martian sky near sunset.

I will reanalyze these frames with less gain in the red channel and

post the results later.

Enjoy,

Mike Snider