Saturn through the obsessionator

Dave Lillis · Post by **Dave Lillis** » Thu Feb 14, 2008 8:53 pm

Well Lads,
Frank and I finally got down to the west coast of Clare last night for a near all nighter (I had today off, poor Frank didn't, I don't know how he went to work today !!

)
While there the seeing was excellent for Saturn, so out came the laptop and the webcam and we got this image. I centred and focused the image while Frank ran the laptop.

The moon Rhea is visible in this image, Dione and Tethys are visible in an over enhanced image, but are too faint to show up well here.
Its about 800 frames stacked from a 3k frame AVI, this was with a 3x teleview barlow and the 20" F5 obsession, there were alot on moons visible also around this image.
Once the moon went down the sky was just incredible, we'll put up an observing report later on this one.
Interesting enough we were unable to get a good one of Mars, it seemed to me that the seeing out over the ocean direction where Mars was worse.

Conn Buckley · Post by **Conn Buckley** » Thu Feb 14, 2008 10:01 pm

Dave, thats an incredible image -- congrats and well done to both yourself and Frank. I see Rhea in the 7 o'clock position. Presumably the scope's motorized system is working well to achieve this. Still, I expect it took a fair bit of co-ordination between ye to achieve this.
With the angle of the rings now it is mighty hard to capture the Cassini division but you have managed it.
I had a look at one of your Saturn images from 2007 (Feb I think) to see how much the 'rings angle' had changed and it is remarkable at how much of Cassini was on view 1 year ago.
I hope you don't mind but I put the two images together to check this. Was last year's taken with the 12"? Conditions would surely be different e.g. max. elevation for Saturn last year was 5 degrees higher which makes your latest image quite remarkable.
I look forward to seeing more images from the 20"Obsessionator.
BTW, be sure to bring this to the next club meeting -- some of our members do not have access to this forum.

Dave Lillis · Post by **Dave Lillis** » Sat Feb 16, 2008 10:00 am

No problem Conn, it is amazing how much the rings have deminished.

I went back and tried to upscale the image abit, I couldn't quite get 2x out of it without getting alot of graininess, but 1.5 actually worked out not too bad.

John O'Mahony · Post by **John O'Mahony** » Sat Feb 16, 2008 10:37 am

Thats a class shot Dave.
Saturn is still hidden at the back or our house at the moment but next month it will be positioned perfectly from my back yard for imaging.
How does the Argo Navis hold up under such high magnification tracking wise??

Dave Lillis · Post by **Dave Lillis** » Sat Feb 16, 2008 5:46 pm

Hey John,
It works pretty well, the occasional gust does wobble the scope slightly especially with the shroud on, there is absolutely no way we could do this level of imaging without the drive system.
The azimuth slow motion is bang on, there is a small lag in the altitude adjustment, I suppose I'll get around to programming the backlash compensation sometime soon.

Conn Buckley · Post by **Conn Buckley** » Sat Feb 16, 2008 7:49 pm

Dave, The extra work you have done really made this image more striking -- even Rhea is clearer -- really great stuff.
I remember reading something once about 'Rayleigh scattering' which I think has to do with the scattering of blue light and it seems to happen at the northern pole on Saturn. Presumably North is down in this image? I can't say I understand enough about this and I don't know why only one pole. Could you enlighten me please?

Dave Lillis · Post by **Dave Lillis** » Sun Feb 17, 2008 1:41 am

Yes this Rayleigh scattering on Saturn is amazing when you consider whats going on.
In the northern hemisphere (bottom in the above images), the dense yellow clouds have sunk towards the planet leaving a clear transparent atmosphere of hydroden above them, enough of a transparent atmosphere to generate a blue sky so giving the planet a blue hue (yes, the sky on Saturn is blue!!), but this is only in the northern hemisphere. In the southern hemisphere the sky is yellow.

I noticed this in images a year or 2 ago as the rings narrowed revealing more of the northern hemisphere and thought that it was somehow an imaging artifact at first, would you believe that it took Cassini reaching Saturn in 2005 to prove conclusively what was causing this effect.
http://science.nasa.gov/headlines/y2005 ... saturn.htm

The latest theory on this is that the rings block out a sizable amount of heat in the northern hemisphere thus causing the atmosphere to contract, so shrinking it and leaving the lighter hydrogen behind on top.