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[Centaur]

Jupiter’s Galilean satellite #1 Io and its shadow will both transit Jupiter during the night of 2011 OCT 27/28. In fact, Io will appear to partially occult its own shadow. Practically speaking, this can only be observed near the time of Jupiter’s solar opposition which will occur later on the 28th. Additionally, during these transits satellite #3 Ganymede will first become eclipsed by Jupiter’s shadow and then become occulted behind the planet.

I’ve created two preview graphics of these events to help you get a better picture in your mind of how these bodies will be positioned relative to each other. Just click www.CurtRenz.com/jupiter

Photos and descriptions of these events would be welcome additions to this thread.

[Paulie pchris00]

I observed both the Io transit/shadow transit and the Ganymede occultation/eclipse. I have decent images, but still need a couple days to go through and pick the best ones, edit them, and post them. I'll try to make this a high priority.

As a tease, here is a shot not long before Io's first contact. Ganymede is upper left, before the occultation.

Attachments:

[Paulie pchris00]

One of the reasons I love observing the Jovian system and our own Moon is that they give us some of the best chances to see the universe in motion, in real time. When I have the time, I love watching those four little dots dance around Jupiter, or watching the terminator creep along the lunar surface. Stellar occultations by the Moon are nice when you can get them, but one of the easiest ways to see our solar system in motion is through the Galilean Satellites. When Curt informed us of not only an Io transit, but an occultation of Ganymede, and an occultation of Io’s shadow by Io itself, I was really hoping for clear skies. Mostly, the sky cooperated with me.

To get the best images I could, I used the 16” LX200 at Conway Observatory. I used my own 25mm 1.25” eyepiece with a 2x Barlow lens, because that particular eyepiece is easiest to use with my point and shoot camera. For most of the images I used a yellow filter (I think #12?) to reduce the glare from Jupiter, without dimming Io and Ganymede too much.

All timings are based on direct visual observations.

Io’s first contact was at 10:19 PM CDST.
Io’s second contact was at 10:23 PMCDST.
Ganymede was noticed dimming, entering Jupiter’s shadow at 10:43 PM CDST.
Ganymede was fully eclipsed at 10:45 PM CDST.
Io’s third contact was at 12:27 AM CDST
Ganymede was observed at 12:29 AM CDST (I was watching intently as Io was crossing Jupiter’s limb, and didn’t observe the exact moment Ganymede reappeared).
Io’s fourth contact was at 12:32 AM CDST.

I’ll let the pictures tell the rest of the events.





Okay, I even threw in some GRS pics at the end for free.

[Centaur]

Thanks for your fine report, Paulie. Glad you had a good time. But the photos don't seem to be coming through. Particular thanks for verifying my predictions seen below.

[Paulie pchris00]

Okay, I hate to do this, but these images have most definitely not been deleted!

It took me 20 minutes to get them all copied and pasted. I don't have the time to figure out what the problem here is, check out the images on my blog. I'll try reposting them here when I get a chance.

pchris00pnc.blogspot.com/2011/10/io-transit-ganymede-occultation-october.html

[Paulie pchris00]

Visual timings are hard, and the seeing conditions left something to be desired. Throw in freezing temps later in the night, and I spent a lot of time waiting down in the heated control room. I need to practice visual timings for, you guessed it, the Venus transit. For visual timings only to the minute, they're pretty good. Now I'm curious to know how close they would have been if I'd timed it down to the second? Maybe not much better given the bad seeing conditions, but I wonder.

I should also note that Io's shadow was visible almost from the moment the transit began. It's usually tough to discern near the limbs, but not last Thursday. Also, Io was visible on Jupiter's disk nearly to the center of the planet. I'd say about the first 1/3 of the transit Io was visible, and the last 1/3 it was visible. I normally can't see the Galilean Moons in front of Jupiter's disk unless they are very near the limb. Maybe using the 16" helped, but I've observed transits & shadow transits with it before, and have never seen a moon so far into Jupiter's disk. My reasoning for seeing Io so long is that by being in front of it's own shadow brought extra contrast, and therefore better conditions to view Io.

Thanks for letting us know these special events, Curt. I try to make a point to observe them when I can. Do you mind if I post your timing chart in my blog post, with a link to your website?