by Ray Cash
Hey, it was a (rare) clear night in San Francisco!
But for those less fortunate--but fortunate enough to have some astro software--there's good news: you can experience the shadow transits virtually with Guide 7.0, Starry Night Deluxe, SkyTools, and perhaps other software too... but these all worked beautifully on my 'puter... Just set the date and time (UT) to Jan 15, 07:00:00, zoom in on Jupiter, and you'll see very nearly what I saw through my scope at 11pm PST last night (Jan 14, 2001).
| Scope | 4" Tele Vue Genesis-sdf f/5.4 refractor on Gibraltar alt/az mount. |
|---|---|
| Magnification | 114x (4.8mm Nagler); 182x (3mm Radian) |
| Seeing | Pretty good, maybe 8 of 10... Views were crisp at 114x; at 182x views were crisp perhaps 50% of the time. |
| Temp | mid 40's |
Set the scope up at 8:30, took a quick peek at Jupiter... Pretty mushy... Don't let anybody tell you refractors don't need to cool down! Ganymede just finishing its transit (egress) and seemingly emerging from Jupiter's south-west limb... The GRS was in that "quadrant" of Jupiter, too... Came back a couple of hours later--MUCH better viewing due to seeing/cooldown-equilibrium! Io's shadow was a very noticeable inky black spot about a third of the way from the planets' western limb, on the SEB; the satellite itself perched maybe five seconds from the west-southwest limb. No sign of Ganymede's shadow, though the satellite wasn't far from Io; just 20 seconds (+ or -) southwest. Around 10:40 pm PST I noticed Ganymede's shadow (that's about two minutes after the predicted ingress)--a very noticeable "notch" on the southeast limb of the planet. From about 10:50 to 11:10pm (PST) both shadows were clearly seen--a wonderful sight! Ganymede's shadow was at least twice as noticeable (big) and clipped the cloud tops of Jupiter much more south and east of Io's shadow; which was basically centered on the SEB, transiting to the western limb. By 11:15, Io's shadow was getting harder and harder to pick out from the limb, and I called it a night.