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  #1  
Old 29-04-2017, 06:58 PM
Tropo-Bob (Bob)
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Ganymede's Shadow

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.
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  #2  
Old 29-04-2017, 08:49 PM
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Tinderboxsky (Steve)
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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.
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  #3  
Old 30-04-2017, 07:57 AM
Tropo-Bob (Bob)
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Quote:
Originally Posted by Tinderboxsky View Post
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.
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.
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  #4  
Old 06-05-2017, 09:27 PM
FedEx (Andy)
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Quote:
Originally Posted by Tropo-Bob View Post
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.
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!
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  #5  
Old 06-05-2017, 10:12 PM
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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.

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Originally Posted by FedEx View Post
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!
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  #6  
Old 06-05-2017, 11:19 PM
bigjoe (Joe)
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re Ganymede

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.

Last edited by bigjoe; 06-05-2017 at 11:38 PM. Reason: adding more
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  #7  
Old 07-05-2017, 09:00 AM
Tropo-Bob (Bob)
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Quote:
Originally Posted by bigjoe View Post
..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..
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 ); 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.
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  #8  
Old 07-05-2017, 09:13 PM
bigjoe (Joe)
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Quote:
Originally Posted by Tropo-Bob View Post
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 ); 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.
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.
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  #9  
Old 08-05-2017, 03:57 PM
Tropo-Bob (Bob)
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Quote:
Originally Posted by bigjoe View Post
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.
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.
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  #10  
Old 08-05-2017, 08:06 PM
kkara4 (Krishan)
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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 .

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!
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  #11  
Old 09-05-2017, 12:03 AM
bigjoe (Joe)
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Quote:
Originally Posted by Tropo-Bob View Post
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.
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
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  #12  
Old 11-05-2017, 07:48 PM
Hemi
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I think Ganymede is doing it again on Saturday night....Is that correct?

Hemi
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  #13  
Old 11-05-2017, 08:23 PM
bigjoe (Joe)
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Quote:
Originally Posted by Hemi View Post
I think Ganymede is doing it again on Saturday night....Is that correct?

Hemi
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

Last edited by bigjoe; 11-05-2017 at 08:38 PM.
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  #14  
Old 11-05-2017, 08:38 PM
bigjoe (Joe)
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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 !

Last edited by bigjoe; 11-05-2017 at 08:39 PM. Reason: add
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  #15  
Old 12-05-2017, 09:41 PM
Benjamin (Ben)
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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
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  #16  
Old 13-05-2017, 06:22 PM
Tropo-Bob (Bob)
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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.
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  #17  
Old 13-05-2017, 09:37 PM
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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?
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  #18  
Old 14-05-2017, 10:48 AM
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Tinderboxsky (Steve)
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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.


Quote:
Originally Posted by Tropo-Bob View Post
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.
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  #19  
Old 15-05-2017, 10:31 PM
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Totally clouded out ��
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.
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