Io transit

by Bill Arnett

At 5:18 AM -0600 10/25/99, Ginger Mayfield wrote:

... Bill, how did it look from California?

Pretty good. I had excellent seeing all evening but, like Leonard, I decided to go to bed about midnight and get up again at 3am to see the transit. When I arose (with great difficulty :-) the seeing was much poorer but still better than average. I could clearly see the shadow and Io just preceeding it across the southern edge of the SEB. I did not see any deviation from roundness of the shadow. The shadow looked bigger than Io itself but that's probably an illusion.

What I saw matched pretty well what Starry Night Pro predicted. SNP shows a little overlap between Io and its shadow but I wouldn't have been able to see that given the seeing.

This was with my homemade 10" f/6 Newtonian with Zeiss/AP/Baader binoviewer, 2x TV Big Barlow and 19mm Panoptics.

Earlier, when the seeing was good, I tried very high magnifications while looking at Saturn. 625x was just fine! 1250x was not any better but not much worse, either, except that tracking a Dob at that power is so much work that you don't get much time to actually observe :-(