dancing with the moons

Hi all,

It has been a long winter and a long time since I've had an image to share - I hope you enjoy this animation prepared from images captured early on Easter morning:

http://www.avertedimagination.com/img_pages/dance_of_tethys.html

(follow the link below the image to compare a monochrome version of the observation.)

I was excited to have a night out under a clear sky after many months of clouds and cold. As I pored through video of saturn recorded in pretty good (6/10) seeing, I noticed a pair of bright and dusky spots moving in tandem. Had I known that a transit of Tethys was scheduled I would have planned the workflow differently. The four frames here are captured through a mix of red, green and IR filters - hence the luminosity variance seen in Saturn's cloud belts. Using a small number of frames (about 200 for each image) and a firm hand in processing I was able to isolate the disk and shadow of Tethys against Saturn - perhaps also Enceladus as it reached the darkened limb just to the left of Tethys' shadow.

A moon transit on Saturn is quite a bit more challenging to record than similar events on Jupiter. Saturn is twice as far from us and Tethys only a third the diameter of Europa (a fifth that of Ganymede.) Tethys subtends about one sixth of an arc second (Enceladus would be about half that size.) But as the plane of Saturn's system aligns with ours and these dances become more frequent events, I expect we will have a chance to enjoy many more of these observations.

best wishes,
Alan

Hi Al, congratulations on capturing Tethys and its shadow transiting a beautiful Saturn, how sweet is that. I knew you had clear skies that evening and figured you would be out imaging, what exquisite timing. That's it, the next clear night I'm going to do a "Saturnian Moon Dance" and hope for the same. All joking aside, I'm glad you were finally able to get out and enjoy the (clear) fresh air. Akira Kazemoto has a similar shot posted over at ALPO-Japan, dated 3-15-08. By the way, excellent moon animation, it does look like they're dancing. Cheers, Dan

Alan, congradulations on capturing that incredible transit! Glad to see the sky finally cleared for you. Looking forward to seeing more of your images. Thanks for posting

Regards,
Steve

Hi Alan, according to JPL's Planet Simulator we will have seven opportunities next season to image Titan's shadow in transit. Here are the dates; 11/20/08, 12/06/08, 12/22/08, 01/07/09, 01/23/09, 02/08/09 and 02/24/09. With that many chances somebody should be able to capture it, what a beautiful and rare "Picture Of The Year" that would make. Does anyone know if it was imaged by amateurs back in the mid 1990's? Have a good day, Dan 8)