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[Centaur]

The shadows of Jupiter’s Galilean satellites #1 Io and #3 Ganymede will simultaneously transit Jupiter during the afternoon and evening of 2012 MAR 15 in North American time zones while Jupiter is above the horizon. Io itself will be transiting at the same time.

I’ve created four preview graphics. One as viewed from above Jupiter’s north pole and a second as viewed from Earth. The third is an event timetable. The fourth displays the dance of the satellites and shadows with Jupiter at 90-minute intervals. They can be seen by clicking www.curtrenz.com/jupiter

Photos and descriptions of the event would be welcome additions to this thread.

[scottmason]

Shot Jupiter last night, one of the photos has to dark lines on the top of the planet..See them? Are these the shadows you mention? If not, maybe just an aberration in the photo. Let me know what you think.

1/800 s ISO 2500 300mm with 1/4X teleconverter F/5.6



Another from last night. Here's Venus and Jupiter together, with details of both.
The "shadow" I got in my photos was different from picture-to-picture. Sometimes a black spot on the planet, the next shot would be on the right side, the next on the left, and so on. Does Jupiter rotate that fast or is it just atmospheric disturbance/low res for my focal length?

[Centaur]

Welcome to the discussion group, Scott.

Sorry, I really can’t make out much in that small mottled image. Possibly that dot near the top is Ganymede’s shadow. I’d really need to know the exact time that the photo was taken and which direction is up.

[scottmason]

Up is "up" in all images..if that makes sense. It's just a telephoto lens on a tripod
First photo was taken at 7:36:16 PM
Second photo (of both planets)at 7:12:05 PM

Thanks!

[Centaur]

I applaud your enthusiasm. I’ll assume those timings were in Central Daylight Time. The transit of Ganymede’s shadow touched the edge of Jupiter’s disk at 18:56:15 CDT and completely exited the disk at 19:14:03 CDT. Io’s shadow was transiting at the time of both photos. However, the digitally enlarged images are of such poor resolution that nothing can be made out. I’d advise against digitally enlarging astronomical images (or any for that matter). What you want is true telescope images with minimal ISO, minimal F-stop, much slower shutter speed and tracking to compensate for the Earth’s rotation. There will be another dual shadow transit during the evening of March 22. You may want to give it another shot then.

[patrickm]

According to SkySafari, at 7:36, Io's shadow (I think) would have been on southern equatorial belt.

Looks very similar at 7:05, but closer to the middle.

Centaur is right. If you crop, only crop to keep scale. Don't do too much blowing up, and do minimal post processing. Never, EVER is "Digital Zoom".

Check the astrophotography section for my recent post about AP artifacts that result from over processing of images. It's tempting, but leave 'em be.

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[Centaur]

Patrick, if the given time of 19:37:57 in your SkySafari image is CDT, then that is Io’s shadow seen on Jupiter’s disk. Ganymede’s shadow would already have exited the disk. Ganymede itself is the bright object near the bottom of the image. Io itself would have been at the very bottom of Jupiter's disk at that time, but I don’t see it on the image.

[patrickm]

Yeah, I caught that and corrected it.

If we zoom further, we get little Io.

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[scottmason]

I should have known better as a photographer. I teach photo workshops, and tell people never to up-res. But, without enlarging it the planet itself was about a quarter inch wide on my screen so I couldn't help myself. I will just have to wait til I get actual scope images.