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Observing and Drawing a Shadow Transit on Jupiter

Lunar & Planetary
When I discovered on the Sky & Telescope web site that a double shadow transit would take place on Jupiter the evening and early morning hours of June 9, 2005, I decided I wanted to try and observe and record the my observations of the Jovian moons Europa and Io as they crossed the face of Jupiter. When I set up my telescope at about 11:30 that evening, I noticed the entire sky was cloudy. According to the NWS (National Weather Service) the weather was supposed to be clear. The clouds were starting to move out by the time the transit of Europaís shadow started to appear at approximately 12:20 AM of June 10th. I had to wait another 20 minutes before I could see through a clear patch of sky to begin my observation and my sketches.

As I began my observation, I could see that the first shadow of the two was just visible on the far right side of Jupiter in the lower of the two equatorial cloud belts. At about the same time I noticed a tiny speck on the far left side of the planetís limb. At first I mistook this to be one of the moons about to disappear behind the planet.

But as time progressed, I realized that the tiny moon was exiting from the face of the planet and that told me that I was seeing Europa and its shadow. Shortly thereafter, a cloud bank moved over the planet and ended my observations for a while.

By 1:20 AM when I ventured outside once again, the sky had again cleared. I knew it wouldnít last long, however, since I saw lightning off to the west. When I found Jupiter once again I could then see 2 black spots in Jupiterís lower belt. I estimate that the two shadows were separated by about one-third the overall width of Jupiter. By now I could also see that Io had joined Europa off the left edge of the planet. Ganymede could be seen on the same side but much farther out from the planet. From what Iíve read, seeing both Europa and Io at the same time that I could see their respective shadows on the face of Jupiter is a rare thing. This realization just adds a nice topper to my observation and sketches of the King of the Planets. A little perserverance and patience rewarded me with a view and a pair of drawings that I'll never forget.
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Observing and Drawing a Shadow Transit on Jupiter
Authored by: bobmoody onSunday, June 19 2005 @ 10:35 am EDT
On the first night of my June ďBasics of AstronomyĒ classes, most of my students had left by around 10:30 PM on June 2, 2005. We had looked at Jupiter earlier to start off that nightís observing activities and we all saw three of Jupiterís four Galilean moons. Shortly before 11:00, we returned to Jupiter for one last look before calling it a night so my last three students could leave for the evening. As I adjusted the focus on Jupiter, I noticed a tiny black spot on the face of the planet. I inserted a higher-powered eyepiece and then a second round, black shadow came into view. A double-shadow transit from two of Jupiterís moons was underway and we all took several minutes to savor the sight. Seeing those pitch black, sharp-edged shadows slowly crossing the face of Jupiter is a thrilling experience.

Without reading my emails late in the afternoon of that dayís classes, I hadnít seen a message from AOAS member Jon Stone trying to alert me to the event. When I did read the message, I also noted that he alerted me of another transit event for the next weekís classes later in the evening on Thursday, the 9th of June. My students didnít stay late enough to see that event, but I asked Jon in my reply to that first email if he would try to watch it and attempt drawing it for a possible short article for our website. What follows is Jonís account of his experiences with the double-shadow transit of June 9, 2005 in his own words with my editing of the story. I hope you enjoy Jonís descriptions

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