May 30, 2009: Titan-sized luck for Titan shadow transit

Greg Parker

I had great views of Titan's shadow transit, but only after the good luck defeated the bad.

Good luck: My 22" Starmaster arrived last week, two months earlier than I had dared hope. It's a marvelous instrument; picking off galaxies in Virgo is like taking candy from a baby compared to my venerable 8" Orion.

Bad luck: I didn't get home until after 10 pm, leaving little time for collimation and cooling. Collimation is a rather big deal at f/3.3.

Good luck: "Home" is at 2400 feet, on Skyline Blvd not far from Oak Ridge observatory. The fog obediently stayed in the valleys until after midnight.

Bad luck: The tracking drive's battery died after a few minutes.

Good luck: The second battery was inexplicably charged.

In the end I had over an hour of observing time across two hours. Seeing was good enough, improving during the first hour as the optics cooled, then deteriorating again as Saturn sank lower and the fog crept higher.

Titan's shadow was immediately apparent, and lost to bad seeing at 230x less than 5% of the time. Over the course of two hours it moved from near the "right" limb to somewhat past the center. It took me at least ten minutes to remember this was not a transit but rather a shadow transit, and that the bright yellowish Titan-like spot nearby was in fact Titan itself.

My sketch of the field includes two cloud bands, the rings' shadow cast on Saturn, Saturn's shadow cast on the rings, and four moons in addition to Titan. Tethys and Dione were "below" the "right" side of the rings; they too moved noticeably with that as a reference, towards Saturn and in the same direction as the shadow.

As the haze gathered around the Moon I trained my new telescope on it for the first time. The unfiltered light from the eyepiece was like a flashlight beam; teardown was delayed for several minutes as my vision recovered. Looks like the old 8" is still good for something.