From: Alan Friedman <alan@greatarrow.com>

Date: April 22, 2009 5:00:10 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Tethys Transit animation, sort of ......

Hi Jim,

I've been working on my data from the night of April 15th and realize I lead you wrong in the CN post. The bright spot that I first thought was Tethys is a small bright storm at the northern edge of the equatorial zone just north of the rings. I see it also in your animation (might help to slow it down a bit!). I couldn't understand why I wasn't able to find the bright spot in the green data - which was pretty good. Now I see that the storm is not visible in green. 

Tethys followed storm on this evening - close by and almost exactly on the same latitude just above the ring plane. I can barely find it in a single processed file. But if I average several together aligning on the position of the moon, it shows up a little better. Tethys' shadow is there too... just barely and just below the ring plane. I'm going to try and average both the storm and the moon onto a single luminance image to create a composite image. The two move at different rates, making the whole thing quite an alignment and processing challenge. Will share pictures soon, which should help to explain this cryptic message.

best regards,

Alan

On Apr 18, 2009, at 11:21 PM, jimchung2338 wrote:

It was good seeing on the night of April 15th and there was a scheduled transit of Tethys starting at just before 9pm and ending by midnight, perfectly timed with the rise of Saturn in Toronto.

http://tech.groups.yahoo.com/group/Astro_IIDC/files/Planetary/TethysTransit2.gif

Shot with C8 at f20 with mono PGR Flea camera and Custom Scientific filters at 15 minute intervals for 80s to collect about 1200 frames. All automated with Applescript using AstroIIDC to both capture and autoguide keeping Saturn somewhat centered on the ccd.

Can't really see Tethys at all until it clears the face of Saturn. Hoping weather cooperates for the Titan transit at the end of the month which should be readily visible.

Jim