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Ganymede Jupiter Near GRS.

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#1 phillip

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Posted 12 June 2021 - 05:02 AM

Juse moments ago...

 

Thought I was a seasoned observor, looked like a beautiful shadow transit close to the Great Red Spot. But checking SkySafari it was Ganymede! 

 

Perhaps exactly what I was seeing as is a huge moon. Any verification Appreciated! Was a disturbance closer to GRS as well. 

 

Past have spotted Jupiter moons entering, usually difficulty seeing them cross my usual experience. 

 

Maybe I got up too early and seeing things, Lol! 

 

Thanks for any reply in advance.

 

XT10 Dob

6mm ortho


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#2 Special Ed

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Posted 12 June 2021 - 06:36 AM

Phillip,

Some of the moons are difficult to see when they are in front of Jupiter but Ganymede is one that is easier to see.  Nice catch.  smile.gif


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#3 phillip

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Posted 12 June 2021 - 06:52 AM

Tnx so much..

 

Confused me as matched a shadow transit. Have caught some of Jupiter's moons entering, but eventually lose them on crossing. 

 

Ganymede was so dark, amazed on its visibility. 

 

Glad to know I wasn't just seeing things, Lol! 

 

Was a Beauty! 

 

XT10, 6mm ortho gave a nice look this morning...


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#4 Nippon

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Posted 12 June 2021 - 08:02 AM

I saw the same thing this morning. Like you said I've seen the moons themselves near the limb as brighter dots but not a moon as a dark dot before. I checked Sky Safari and magnified Jupiter and what it appeared to show was Ganymede as a bright spot but as I magnified it changed to a dark and featured image of Ganymede. I wondered if perhaps I was seeing Ganymede's shadow directly behind Ganymede itself. But how could that be with Jupiter not near opposition? So I'm thinking the dark dot was Ganymede and it's shadow was cast beyond Jupiter's limb. I too saw a "disturbance" near the GRS and during moments of good seeing it appeared as a dark area of the adjacent band swirling in to the GRS. Also the GRS itself seems to have become more pale than I remember last year when it was quite a saturated salmon color. All in all a nice early morning. 



#5 phillip

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Posted 12 June 2021 - 08:11 AM

Great you also caught It! Yes I had the same exact impressions of what could be happening. 

 

Indeed the GRS is fading. Believe I've read in mere few more decades it will be much less, even vanish. So Sad! 

 

Again great you caught the view! 



#6 Nippon

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Posted 12 June 2021 - 01:29 PM

Decades ago when I first had a good telescope that could show nice detail on Jupiter I remember reading that the GRS was much less prominent then it had been years earlier. It seems the color saturation comes and goes. It was referred to as the Great Red Spot hollow then the color returned.



#7 DirtyRod

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Posted 12 June 2021 - 02:28 PM

i guess I better go recheck mine. I captured a few images and noted what I thought was Ganymede's shadow to the left of the GRS. Sounds like it wasn't the shadow. 



#8 Dave Mitsky

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Posted 12 June 2021 - 03:00 PM

It was indeed Ganymede and not its shadow.

06:22 UT, Ganymede's shadow leaves Jupiter's disk.
07:56 UT, Ganymede begins transit of Jupiter.
11:32 UT, Ganymede ends transit of Jupiter.

 

https://skyandtelesc...cript-utility/#

 


 


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#9 Dave Mitsky

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Posted 12 June 2021 - 03:11 PM

Here's a screen capture from Stellarium showing Ganymede's position at ~5:30 a.m. EDT (9:30 UT).

Attached Thumbnails

  • Ganymede and the GRS 6-12-21 Stellarium.JPG

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#10 phillip

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Posted 12 June 2021 - 05:04 PM

Nice!

 

Cool it was right next to the GRS. 

 

A beauty Indeed! 

 

Tnx all on the verifications ! 


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#11 Redbetter

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Posted 13 June 2021 - 04:50 AM

Ganymede was definitely visible near the GRS at the time.  Seeing was mediocre at the time, so resolution was poor and variable.  I saw the same thing, assumed it was a shadow at first, but perplexed by the rather low albedo difference that resulted in a very weak pseudo-shadow.  I suspected it might be the "missing moon" but couldn't check until I got home.



#12 phillip

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Posted 13 June 2021 - 07:49 AM

Seeing was near average here, was some unsteady but also times of stability. However had a clear view, better than my poor visuals. 

 

Was studying also an activity region at corner of the GRS Red Spot. Wasn't huge but quite noticeable. 

 

My view on Ganymede looked very much like the shadow transit, thought for sure that's what it was till I rechecked my simulator. 

 

Sky conditions can vary alot. Sometimes best view is 130x, more often 160x to 180x works well. 200x was ok on my medium sky tho noted clarity. Exceptional sky nearly no limit goes to plus 400x, however those are exceedingly rare indeed! 

 

XT10, 6mm ortho used this observation

10mm Baader, 8mm Clave, 4.8mm Nagler


Edited by phillip, 13 June 2021 - 07:54 AM.


#13 Cfeastside

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Posted 14 June 2021 - 08:05 AM

Cool i saw this as well and thought it was the shadow.  Thanks for posting!



#14 Mark Gingrich

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Posted 15 June 2021 - 02:10 PM

Someday, I hope to see an image of Jupiter and its Great Red Spot -- with the shadow of one of

its moons centered precisely on the GRS.  Appearing like a bloodshot eye with a dark pupil, how

spooky would it be to have a cyclopean Jove staring back at us?

 

Alas, if the GRS weren't so darn drifty in longitude, it might be possible to predict the next such

occurrence well in advance.



#15 Dave Mitsky

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Posted 16 June 2021 - 01:45 AM

Speaking of Ganymede, there's a great image of it displayed on the APOD for June 14th.

https://apod.nasa.go...d/ap210614.html


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#16 Dave Mitsky

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Posted 16 June 2021 - 01:58 AM

https://solarsystem....ymede/in-depth/



#17 Asbytec

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Posted 21 June 2021 - 10:32 AM

I believe the moons contrast with the underlying cloud, belts or zones, can make or break visibility of the moon transiting across the disc. Moons are easier to see near the limb due to limb darkening effect. When the moon transits over a darker cloud belt, they are often very low contrast and difficult to see. Against a lighter zone, they can be more easily seen as being darker and higher contrast against a lighter background. Once during opposition, though I could not see the moon, I managed to infer Io transiting over a darker belt because it was partly obscuring it's own shadow. Quite a site, too.

By the way, some of the high contrast detail on Ganymede itself, seen in the links Dave provided, can be detected in a modest aperture in better than average seeing and relatively high magnification. Ganymede must be well placed with those features facing Earth, but it can be done. More folks should try it, one day this will be common knowledge. The Jovian moons are not just tiny discs.

Edited by Asbytec, 21 June 2021 - 10:39 AM.



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