From: "sandybumgarner" <sandy@vbbn.com>

Date: October 3, 2005 8:31:05 PM MDT

To: Astro_IIDC@yahoogroups.com

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

Hi Mike,

I did enjoy!

Damn fine shootin'!

Sandy

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--- In Astro_IIDC@yahoogroups.com, "Michael T Snider" <snidermt@a...> wrote:

Hi All,

There was a rare night good seeing in Hershey on Sunday morning 

November 2. Seeing  approached 8 of 10 on the Pickering scale (4 of 5

on the Danko scale).

Images are on my website at

http://homepage.mac.com/snidermt3zp/PhotoAlbum28.html

First is summary collage of Mars. Using the 7" Questar at f/35 via

Barlow projection at the axial Cassegrain focus, I took 2000 frames 

over 67 seconds with both the Sony XCD- X710CR camera for color 

and with Sony XCD-X710 camera for monochrome near infrared.  Also 

attached is a stack of the first 12 sequential frames of 2000 in a

QuickTime movie of Aldebaran superimposed on the first 12 sequential

frames of 2000 of Mars, both at f/35. Note the 1st diffraction ring

on Aldebaran. Also shown is the Mars Previewer II simulation.

Hesperia can easily be seen between Mare Cimmerium and Mare 

Tyrrhenum.  Also seen is Syrtis Major and Hellas.  Similar views

were seen visually through the 7" Questar at 300X and 600X using a

Wratten 21 orange filter.  Detail in the frame stacks approached 1.2 

arc.sec in the IR and about 0.8 arc.sec in the visible.

What limits the detail with my current setup?

Aside from primary mirror diameter, figuring accuracy and seeing, it 

appears that the effect of atmospheric  dispersion is still large

with objects at an altitude of 65°.

Attached are greatly enlarged images of stacks of the sharpest 10% 

of the diffraction pattern of Aldebaran before and after RBG pane 

shifts to minimize atmospheric refraction. Note the vertical

elongationin the diffraction disc separating into red at the top and

blue at the bottom.  This vertical elongation is only partially

corrected by shifting the RGB panes. Note the concentric rainbow 

halo formed by the overlap of the red, green and blue of the1st 

diffraction rings of each color. Red is greater than red which is

greater than green etc. as predicted by wavelength. The diffraction

disc is still slightly distorted even after RGB pane shifting.

Greatly enlarged diffraction patterns are shown for infra-red, the

red pane, the green pane and the blue pane of Aldebaran. Note the 

decrease in disc and first diffraction ring size as wave length

decreases.  Vertical disc distorsion also decreases with decreasing 

wavelength.

Better resolution with the 7" Questar at this opposition may require

Rissley prisms to correct further the atmospheric refraction within

the transmission range of the infrared, red, green and blue filters

used.

Even with Mars at an elevation of 65°!

Enjoy,

Mike Snider