Posted By Dave Mitsky
The transparency varied from bad (i.e., mostly cloudy) to mediocre but the seeing was excellent. In fact, I was quite surprised at just how good it was. The shadow of Io was a sharply defined black spot that crept slowly along Jupiter's equator. I was able to push the magnification to as high as 404x (16mm Brandon) but 249x (26mm Tele Vue Ploessl) provided the best overall view. Other magnifications used were 162 (40mm University Optics MK-70), 202 (32mm U.O. Koenig-II), 216 (28mm Edmund Scientific RKE), 259 (25mm MK-70), and 381x (17mm Pro-Optic Ploessl). The size and brightness differences of the Galilean satellites were quite apparent.
The shadow crossed the CM at about 10:40 p.m. EST (3:40 UT). About 3 minutes prior to the end of Io's transit (4:01 UT) I could make out the shape of Io as it neared Jupiter's preceding limb. By 4:03 UT Io had pulled far enough away from Jupiter that I could see a gap. As the gap widened the fact that Io was casting its shadow on the cloud tops of its parent planet grew increasingly evident.