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[Centaur]

I’ve determined that during the predawn hours of Wednesday, December 31, Jupiter's Galilean satellite #2 Europa's shadow will annularly eclipse/transit #3 Ganymede. The center of Europa's shadow will appear closest to the center of Ganymede at 04:58:32 CST (10:58:32 UT).

I’ve created two preview graphics and a timetable for the event. They can be seen at:  CurtRenz.com/jupiter.html

If older data appear on your screen, I suggest refreshing/reloading the webpage.

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

[Paulie pchris00]

Should be mostly clear tonight. I'm on it.

[Centaur]

Dec 30, 2014 11:25:37 GMT -6 Paulie pchris00 said:

Should be mostly clear tonight. I'm on it.

I appreciate your dedication, Paulie, on what will be a cold night. Keep in mind that Europa is considerably smaller than Ganymede, so unless you have powerful equipment, all you should notice would be a slight dimming of Ganymede. I look forward to your report. Good Luck. 

[Paulie pchris00]

1. Once I get done bowling, I'll be heading down to Conway Observatory. I'll turn the heat on inside, and get dressed in layers, so I'll be okay with the cold.

2. It's not like I have anything better to do, and I really need to stay up all night to get my body back on a sleep cycle before I go back to work next week.

3. I was planning on using the observatory 16" scope, and push the power as much as I can. I wasn't really expecting to see Europa's shadow on Ganymede, but rather just Ganymede dimming. Maybe if I'm lucky I can push the power enough to see the shadow, but I'm not really expecting it.

Full report as soon as I can get it posted.

[Paulie pchris00]

Just watched Io get eclipsed by Jupiter's shadow. It is colder than I expected, and the wind just picked up quite a bit. I was waiting to open the roof until later, but with this wind, I'm not going to chance it. Going to pack up, head home, and observe what I can from there. At the very least I won't have the wind whipping right across miles of barren fields.

[Paulie pchris00]

Well, observing from home with just my 6" Dobsonian, all I can say for certain is that I did not see Europa's shadow directly on Ganymede. I'm not sure if any of my images (afocal from my cell phone) will help determine any dimming, but while annularly eclipsed, I determined Ganymede to be brighter than Europa, and possibly brighter than Io.

And I can't feel my big toe on my left foot. It's cold.

[Paulie pchris00]

Feeling is coming back in my toe now.

[Paulie pchris00]

And whoever says the Great Red Spot is shrinking sure didn't see it this morning. I missed it as it transited the center of the Jovian disk, and was nearing the limb on the side of Europa and Ganymede, but it stood out better than I've seen it in quite a long time.

Thus endeth the observation. Will try to edit images for posting as soon as I can, hopefully by tomorrow.

[Centaur]

Thanks, Paulie, for your fine reports from observing Jupiter and its satellites last night. Now during this cold day drink some hot chocolate and stay warm inside. Tonight, Wed-Thu Dec 31-Jan 1, Io and its shadow will both transit Jupiter. Tomorrow evening, Thu Jan 1, Europa will partially transit Ganymede. I've already posted preview graphics for the latter; the timetable will be updated around midday tomorrow: www.CurtRenz.com/jupiter

[Paulie pchris00]

Ganymede and Europa are currently hiding in Jupiter's shadow, and I directly observed Europa entering the shadow. With Io beginning a transit in less than an hour, for those of us in the Central Time Zone (GMT -6), Callisto will be Jupiter's only moon visible as we begin 2015.

[Paulie pchris00]

Sorry for posting something old so late, but since this is the only time I've observed an annular eclipse of a Galilean Moon by the shadow of another Galilean Moon, I feel it's important to post. I can't find my notes on the weather conditions, but it was damn cold on that last morning of 2014, with the temperature in single digit Fahrenheit, with below zero windchill factor. It was very uncomfortable, but this was an event I did not want to miss.

I started my night at Conway Observatory in Lowell, Indiana, planning to use the 16" telescope to observe the annular eclipse of Ganymede by Europa's shadow. However, windy conditions kept me from opening the roll-off roof. After observing Io disappear into Jupiter's shadow with my 6" Dobsonian, I packed up and went home, hoping to at least avoid the brutal wind across open fields.




Luna in the midnight hour.






Shortly after Io is totally eclipsed by Jupiter's shadow.


After arriving home, I didn't see much sense in sitting out in the cold until the Galilean events I wanted to document were about to start. Here are Curt's graphics from that night, which I downloaded to both a storage disk for my computer, and my phone to use during the observation. (Sorry, Curt. These are very good, and quite useful, and I feel they should be archived with the observation).











I bundled up and went outside to observe around the time Io emerged from its occultation behind Jupiter, which occurred at 4:18 AM CST. By the time I started imaging, it was already visible.




Io after emerging from occultation.


As stated earlier in the thread, I really didn't expect to see Europa's shadow directly upon Ganymede, especially with the limited aperture of my Dob. Pushing the power on the 16" at Conway, maybe I could have directly observed the shadow, but all I really expected to see was Ganymede dimming slightly. Now that I was restricted to observing with just 6" of aperture, I was sure I had no hope of directly observing Europa's shadow, no matter how much I pushed the magnification. During most of the annular eclipse, I tried observing visually, rather than obtaining images, relying on my skill as an observer over the camera on my phone. I did, however, try to get some images while Europa's entire shadow was upon Ganymede to compare brightness before, during, and after the eclipse.

Visually, Ganymede didn't dim as much as I expected it might. Even during mid-eclipse I judged Ganymede to be brighter than Europa, which appeared nearby, and maybe Io, on the other side of Jupiter, and more difficult to compare brightness. Callisto, farther beyond Io, was out of the field of view much of the time I was observing, so I made no attempt to compare the relative magnitudes of Jupiter's two largest moons.




The eclipse had begun two and a half minutes earlier. I didn't take another image until shortly after mid-eclipse, over ten minutes later.




One minute, nineteen seconds after mid-eclipse, and 1:41 before the end of annular eclipse. Ganymede appears noticeably dimmer than before and after eclipse, but still slightly brighter than Europa.




About a minute before the end of annular eclipse.




Eighty-nine seconds after partial eclipse phase ended. Ganymede appears unquestionably brighter than during mid-eclipse.








About 20 minutes after the end of partial eclipse, and over 30 minutes past mid-eclipse.


Observing and documenting the eclipse was difficult, only 24 minutes and 7 seconds from beginning to end, and only 6 minutes of annular eclipse. Time raced by during the annular phase, as I tried to observe visually as much as I could allow, then fumble with my phone in the frigid air trying to image the event. Without Curt's advance notice, I doubt I would have even noticed that Ganymede had been eclipsed at all. Still, fighting the harsh winter conditions, and the poor quality of afocal cell phone images, I think I was able to document the Ganymede had indeed slipped through Europa's shadow.




Only a fool or a dedicated observer would have been in out the extreme cold so long. Or maybe both.