[ATMoB-discuss] Sunday night Saturn

[John Boudreau]

Hi Gary,

That's a common effect I've seen in many Saturn images. I think the effect is real as it's somewhat visible in the unsharpened raw stacked image, but like other features it's contrast gets enhanced during processing.

I think Steve's nailed it. It's *probably* due to the slight translucence and scattering of  Saturn's upper atmosphere. 

I also checked that general latitude region on the original TIFF image with Photoshop's eyedropper tool and the RGB balance strongly shifts towards the blue at the limb, noticeably more than at surrounding latitudes, so blue scattering appears to be a real component there.

And since it's near the limb _and_ has a bright ring backlighting the upper atmosphere, the blue scattering is probably stronger in that region. 

---John

----- Original Message ----- 
From: "Steve Beckwith" <stevebeckwith at comcast.net>
To: <gdjacobson at verizon.net>; "'John Boudreau'" <jeboud at comcast.net>; <atmob-discuss at atmob.org>; <nsaac at nsaac.org>
Sent: Wednesday, March 28, 2007 8:45 AM
Subject: RE: [ATMoB-discuss] Sunday night Saturn


> Gary,
> This doesn't look like an artifact.  It "may" be the rings behind the
> planet being viewed through it's upper atmosphere.  Note the emphasis on
> "may"...
> 
> - Steve
> 
> -----Original Message-----
> From: atmob-discuss-bounces at atmob.org
> [mailto:atmob-discuss-bounces at atmob.org] On Behalf Of Gary Jacobson
> Sent: Wednesday, March 28, 2007 6:03 AM
> To: 'John Boudreau'; atmob-discuss at atmob.org; nsaac at nsaac.org
> Subject: RE: [ATMoB-discuss] Sunday night Saturn
> 
> Excellent photo, John!
> 
> Any comment on the artifact on the left side of the planet where it
> intersects
> the rings? There is a blue tinge and an out-of-roundness of the image.
> 
> Gary Jacobson
> 
> -----Original Message-----
> From: atmob-discuss-bounces at atmob.org
> [mailto:atmob-discuss-bounces at atmob.org]
> On Behalf Of John Boudreau
> Sent: Monday, March 26, 2007 10:35 PM
> To: atmob-discuss at atmob.org; nsaac at nsaac.org
> Subject: [ATMoB-discuss] Sunday night Saturn
> 
> 
> After several months of very poor seeing conditions, I was finally
> treated to a
> couple of hours of excellent seeing on Sunday night and managed to
> capture
> several good webcam videos of Saturn. Here's the result from the best
> RGB
> filtered video sequence, taken with my Celestron 11 and monochrome CCD
> ToUcam
> webcam working at about f/26 with a Barlow:
> http://home.comcast.net/~jeboud/saturn_032607_0146UT.jpg
> 
> Hope others got a chance to enjoy the seeing conditions!
> 
> ---John Boudreau
> 
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>