Sunday, August 17, 2008

Fantastic open night

Saturday night was the occasion for the monthly Open Night at Stephens Memorial Observatory (SMO). The advertised object for viewing was Jupiter. By the time the two-hour event was over more than 134 visitors had entered the dome and looked at the giant planet through the big telescope! I could not believe it; what an incredible turnout! Seeing conditions varied from fair to very good but most visitors got decent views of our Solar System's largest world. The two major cloud bands were nearly always visible and often distinct and many viewers reported seeing, as did I, additional bands in Jupiter's cloud tops at 104X. We were able to see the four Galilean moons: three strung out on the right side (as seen through the eyepiece) of the planetary disk --Io, Ganymede, and Callisto in order moving outward-- and Europa close by the limb on the opposite side alone. Europa entered occultation at 9:36 PM EDT when it moved behind Jupiter. I've seen the Galilean moons many times before but never had watched an occultation even in stages (between visitors' turns at the scope). The final visitors of the night were also treated to spectacular views of Earth's own brilliant Full Moon, each filing out of the dome happily impressed. I had changed from my 32mm Plossl to the fist-sized low-power eyepiece for a full-disk view. That old occular must have a focal length of close to 100mm to offer that kind of image -- I really need to measure it one day! Closed up a little after 11:00 PM hoarse, tired, and excited. It was an fantastic open night.