Ganymede's Shadow

[Tropo-Bob]

Tonight, I had a quick peek at Ganymede's shadow, which was near the edge of Jupiter's disc and close to Jupiter's Polar region. This was a nice example for me of the 3D reality of Jupiter's Moons.

The ability of the shadows of the outer Moons to be anywhere on Jupiter's disc surprises and delights me. Its a nice change from seeing the more frequent eclipses of the inner Moons with their shadows always being far closer to the Equator.

[Tinderboxsky]

I was watching the shadow transit and egress this evening too. My first observation of the shadow was about 30 minutes before egress and yes it was quite close to the northern polar region which certainly shows up the 3 dimensional nature of our solar system.
I then returned about every 5 minutes to see the shadow gradually approach the limb. For the last 5 minutes I observed continuously to see the shadow kiss the limb and then gradually form a notch in the limb. The half way point was quite clear and then the notch gradually decreased and eventually disappeared as the shadow moved away. I enjoy the sense of motion in our solar system that these observations reveal.
Seeing was good and transparency poor but good enough. I was observing at 160X: VixenNA140SS with LVW5.

[Tropo-Bob]

Steve, thank for adding your interesting observation. I should have kept watching, although we all have a chance to see it in reverse on May 6th when Ganymede's shadow makes ingress at 8.26pm.

[FedEx]

Thanks for mentioning that this could be seen tonight, i had forgotten i had set an alarm after reading this last week. It has been quite cloudy but through the gaps I managed to see the shadow from 8.40pm, a first for me. I didnt realise how quickly jupiters moons whizz around, but could see the movement of Ganymede which was almost touching jupiter when i first looked.

I have realised to slow down and really see what im looking at, Ive looked at jupiter maybe 10 times but only for a minute or two. Over the last hour I have seen so much more, even through the clouds!:thumbsup:

[Tinderboxsky]

Good catch Andy. I was clouded out here.
Yes, time at the eyepiece will reveal so much more. Observing motion in what otherwise is thought of as a static sky interests me. There are many transient events that one can observe over relatively short time frames that reveal motion in the sky.

[bigjoe]

Only had a quick look myself Bob and Steve and Fedex ..It was awfully close to the polar region saw some obvious bluish regions (Festoons) in and extending out of the main belt nearby, in ordinary seeing with Etx125 and 13mm nagler, here in Concord..Then had to rush out for a late dinner; absolutely fascinating to watch ..need to observe these events more often.

[Tropo-Bob]

The Shadow certainly was close to the Pole. Europa's shadow goes over Jupiter on Monday evening (8.20 to 10.46). I will watch with interest to see where its shadow fall in comparison. Clouds permitting ( I only saw the Shadow for 2 minutes last night, then cloud, then rain :shrug:); I will also look for Europa reappearing after Transit at 9.20ish.

I noticed last night that Ganymede could be detected reappearing outside of Jupiter's disc some 2 minutes earlier than the prediction. Anybody know how these predictions work? Is it the middle of the moons disc crossing the Jupiter's edge that is used for the prediction? I am guessing so and that is why I could see the edge of the moon clear Jupiter earlier than the predicted time.

[bigjoe]

Weather permitting Bob, I'm going to roll out the 254mm Sct on the Celestron AVX mount.. just got it from Bintel ,and have a good look at it, and also those unusually bright bluish Festoons!
Cheers bigjoe.

[Tropo-Bob]

Good luck Joe. It sounds like an impressive set-up. Love to hear about your observation. Weather here is looking like at 50-50 chance of seeing Jupiter tonight.

[kkara4]

i'm really glad i found this thread - despite being primarily an imager it really is something special to see all these events through the eyepiece. I can only imagine some of your reactions to a live video feed with one of the modern cameras, though i understand it no longer becomes strictly visual :P.

i was able to image half of the transit, the rest i just watched it through gaps in the clouds. it really is fascinating to think you are watching a solar eclipse on another planet!

[bigjoe]

Poor weather tonight Bob with clouds etc ..but glimpsed it in the Northern Equatorial Belt ; quite hard to find really in the ETX first around 1130pm in middle of the belt ..needed power used a 13mm Nagler first up ..no sighting at all ..swapped to a Barlowed 17.3 Delos for a sighting, then a 9.7mm Plossl.. much easier in the 10" SCT on the AVX MOUNT! ; still difficult to observe and no where near as obvious as Ganymede's shadow transit!
Did anyone else see this in good seeing?

bigjoe

[Hemi]

I think Ganymede is doing it again on Saturday night....Is that correct?

Hemi

[bigjoe]

Hi Hemi . Need to check ..I thought Ganymede maybe a daytime occurrence, and only Io at night about 8 20 shadow transit.
Ganymede casts a big unmistakable shadow , its the best to watch.
Maybe someone will add further to this!
PS: JUST CHECKED ..YES 21:16 EST
Cheers bigjoe

[bigjoe]

Transit of Ganymede ..Ingress at 21:16
Does not appear to be a shadow transit till 00:25 on 14th ..so keep a watch for it !

[Benjamin]

Slightly off topic (not Ganymede) but this post got me scanning through Sky Safari and it seems Io and Europa are working together on their shadow transits, a few of which are in observable hours, although it looks like it might be hard spot Europa's shadow. First one I could find was 3am on May 23rd, then 5am May 30th, 7pm June 2nd, 9pm June 9th...

I'm an infrequent watcher of these things so maybe this is all too common, but it's interesting to see how all these moon shadow transits time with each other. Thanks for the post :thumbsup:

[Tropo-Bob]

Another shadow event tonight, but at 12.25, it will be too late for me. (I am working tomorrow.)

However, Ganymede transits in front of Jupiter from 9.16 this evening. I have heard that Ganymede is one of the easier Moons to watch pass in front of Jupiter. Worth a try if the weather holds.

[LostInSp_ce]

I'm watching it as we speak (I hope to get some images as well). I did see something else interesting about an hour ago at 8:15pm passing in between Jupiter and Europa it looked like a satellite but I couldn't be sure. I tried to capture it but it moved out of view too quickly. Anyone else see this or know what it was?

[Tinderboxsky]

Totally clouded out 😡 I did manage to follow a Ganymede transit last year in very good seeing conditions. I watched the final approach to ingress and the ingress continuously, then revisited the transit stage every ten minutes and finally watched the egress stages continuously.

[LostInSp_ce]

We had some light cloud but were still able to observe between 12-1am. We also tried to do some imaging but it didn't turn out too well.

[Tropo-Bob]

Jupiter's Moons are eventful tonight!

Earlier this evening, I saw the unusual sight of 3 Moons close to Jupiter's disc. Europa was then occulted and Ganymede slowly disappeared into shadow. At 8.20ish, Io commences a transit and that leaves only Callisto visible until Ganymede reappears from being eclipsed at 20.50ish.

I hope the weather holds!

[Tinderboxsky]

Yes, a busy night. Thanks for your report Bob. I usually try to catch these busy sets of events but was completely clouded out.

[Tropo-Bob]

Thanks Steve,

There are a few busy nights coming up. On June 2nd, shadows from 2 Moons will be on Jupiter at the same time and there are various events on 31st May.

Tonight, Io reappears from Jupiter's shadow around 8.40ish

[Tinderboxsky]

I will definitely be out observing on 2 June. I am in Melbourne at the moment without any telescopes so won't see anything at the moment.
We have just picked up a new Cub camper trailer as we want to extend the range of our regular road trip holidays. So much room after being regular tenters for many years!

[Benjamin]

Child, mother-in-law and I had a great view of the double shadow transit of Io and Europa just now. A bit late for the young one to watch too long but the spatial sense you get of the moons and their relative distance from Jupiter is quite something. Was very happy to see this clearly through my f9 ED100 at 150X.

[Tinderboxsky]

Well done Ben and so envious. Had great plans to observe but foiled by heavy cloud.

[Saturnine]

Was really looking forward to tonights double shadow transit but right on cue had wall to wall cloud the entire time and now that it is over the cloud is breaking up again.
There will be double transits again, for the east coast, on the 9th & 16th, so surely one of those evenings have to be clear, please. Willing to sacrifice a scope if it will help.

[Tropo-Bob]

It all happens again tonight from around 8.20ish. Ganymede throws the most distinct shadow of all the moons on Jupiter. Steve's observation, which I have quoted has inspired me to be particularly interested in the first few minutes when the shadow touches the disc of Jupiter, before the full, round shape of the shadow has not yet formed.

Clear skies everyone!

[Tinderboxsky]

I will be interested to hear how you go Bob.

The ingress is occurring on the limb facing away from the sun, so it will be less well illuminated, reducing contrast. My observation was an egress on the brighter limb.

It looks like it will be clear here too, so shall hopefully give it a go.

[Tropo-Bob]

The first indication of a shadow was seen at 20.16. From there it grew into a reverse C and finally looked circular. However, it was 20.28 before I was fully satisfied that the shadow was within Jupiter's limb. It reminded me of seeing Mercury transit over the sun and I wondered whether I was seeing a black dot affect (unlikely though). The shadow was closer to the pole than the equator so was not entering the limb at a perpendicular angle. Ganymede's large size and the glancing angle may explain why it took so long. There is also the illumination affect that Steve mentioned. Alas, the seeing was also ordinary.

Nevertheless, the weather looks good, so I may try for the exit at 10.30ish.

[Tinderboxsky]

It sounds as though you have done well given you thought the seeing was ordinary. What scope and magnification were you using.
Down here it was a brilliantly clear night with high transparency but alas abysmal seeing. Jupiter's disk was boiling even at only 62X. Not a chance of seeing the shadow ingress.
I contented myself with some low power exploring of the hidden gems in and around Carina.

[Tropo-Bob]

The reversal was also a slow affair, with the shadow touching the limb at 22.18 and finally exiting at 22.29. (Note, I amended my previous post, as I made a typo re the time)

I used my Vixen 115mm and a 7mm Delite EP (127x).

Steve, Carina certainly is a lovely area, where the more U look, the more U find!

[Tropo-Bob]

Jupiter has all 4 major moons on one side tonight, also extending out as per their orbits distance from the planet. (Io closest, then Europa, Ganymede and finally Callisto.)

[Tropo-Bob]

Ganymede's shadow will be again be on Jupiter tonight from 8.15ish.

As this is the largest and easiest-to-see shadow of any of Jupiter's moons, it is well worth a look!