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  #1  
Old 12-05-2018, 08:13 AM
Tropo-Bob (Bob)
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Jupiter Moon Events

I observed Ganymede eclipse disappearance on 10th May and Europa reappearance out of eclipse on 11th May. Both of these events happened very close to Jupiter's limb, as would be expected since Jupiter was in Opposition on 9th May.

Ganymede.
I followed Ganymede's disappearance with 2 scopes. I commence observing with a Tele Vue Ranger using 68x on an altz mount. However, I became nervous about having sufficient light grasp and the possible difficuties of observing the event, so I also setup a 5" SCT with aprox 100x on an EQ5 mount.

Observing the dimming of Ganymede was difficult because of its closeness to Jupiter's limb. It was a bit like trying to resolve an equal double star. I kept swapping from scope to scope. The view was cleaner through the Ranger with with a tiny, sharp point appearing next to the limb. It was a little easier to see with the SCT because of the extra magnification and light grasp, even with the trade-off of the view being less sharp. Ultimately, it did not make much difference. Ganymede was visible in both scopes at 21.21 and disappeared in both scopes at 21.22.

Ganymede disappeared close to Jupiter's south pole. For a while, I actually wondered whether it would not pass behind Jupiter's disc, but only disappear into the shadow.


Europa
I used my new (but secondhand) Vixen ED 81mm to view Europa's reappearance out of eclipse. Two evenings prior, I had view Europa transit across Jupiter below the northern polar region. Thinking of how Jupiter's plane is currently offset to us, I then deduced that it would reappear on the same side below the southern polar region. I also wondered if I would see the moon brightening, or whether it would just appear close to Jupiter's bright limb.

Using 125x, Europa just appeared when at or near full brightness, but at least it appeared where expected.


Future events:
Tonight (12/5): Io has an occultation at 22.57, reappearing tomorrow at 1.11.
Tomorrow (13/5): Io has transit and shadow events from 20.16 to 22.32.
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  #2  
Old 12-05-2018, 10:35 PM
Tropo-Bob (Bob)
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Io occultation

Io
I viewed the occultation of Io this evening with my Vixen ED81 using 90x.
Using a lower magnification 33x, I had difficulty keeping sight of Io some 5 minutes before the occultation was completed, so switched to a more appropriate magnification.

It disappeared completely from view at the predicted time (22.57) and was located a fraction to the south of the South Equatorial Belt.

So when Io returns for its transit tomorrow evening, I assume that when it begins crossing Jupiter's limb, if will be just to the north of the North Equatorial Belt.

From what I have noticed in the last few days, shadows of Jupiter's moons appear on the disc a little to the south of the Moon in transit. Thus, if I have this right, Io's shadow during the tomorrow transit will probably be on the northern edge of the North Equatorial Belt. I will be looking to see if I have this right (weather permitting).

Future events:
Tomorrow (13/5): Io has transit and shadow events from 20.16 to 22.32.
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  #3  
Old 14-05-2018, 09:45 AM
Tropo-Bob (Bob)
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Io transit

Quote:
Originally Posted by Tropo-Bob View Post
Io

So when Io returns for its transit tomorrow evening, I assume that when it begins crossing Jupiter's limb, if will be just to the north of the North Equatorial Belt.
Io
Hazy clouds greatly distorted my view of last night event, however, I was able to confirm that Io transited across Jupiter, just north of the North Equatorial Belt. I could barely see the shadow because of the haze, but it did appear to straddle the northern edge of the same Belt. (Using Vixen ED 81mm with 90x & 125x)

Future events, which I will attempt to view:-
14/5 19:40 Io eclipse reappearance
14/5 Callisto passed to the north of the Jupiter around Noon, I will observe how far Callisto's current position is from the planet.

18/5 0.40 Ganymede occultation disappearance.
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  #4  
Old 14-05-2018, 10:09 AM
Saturnine (Jeff)
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On the 16th beginning at 23:56 is a shadow transit of Europa, moon ingress at 23:37 EST. Red Spot crossing the central meridian at 22:22, so a chance to see the shadow ingress as the Red Spot is heading for the limb. Weather forecast for this week is more favourable than the past several days down here.
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  #5  
Old 14-05-2018, 07:28 PM
Tropo-Bob (Bob)
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Io Eclipse reappearance

Io
Using an 8" SCT (95x), Io was glimpsed Io reappearing at 7.38pm adjacent to the South Equatorial Belt. The red spot was also visible in from the Jupiter's limb.

There was a small, but definite separation of Io from the disc of Jupiter when it reappeared. This separation will grow larger in future, as the planet moves away from Opposition.

Callisto, Ganymede and Europa were on the opposite side of Jupiter. It was a little strange to see them in reverse order from Jupiter: Callisto, Ganymede and Europa being furthermost.

I attempted an estimate of how far Callisto's orbital plane was north of Ganymede's. I thought about the same as the distance between the polar edges of the Equatorial Belts, or about 40% of the North-South diameter of Jupiter. I hope to test this by seeing Callistro pass Jupiter's South Pole by approximately this distance on the evening of 22nd May, at about 6pm. (Ganymede is only just inside Jupiter's disc at the pole when it passes, so Callistro should be approximately 35-40% of Jupiter's polar-diameter further out.)


Future events, which I will attempt to view:-
18/5 0.40 Ganymede occultation disappearance.
21/5 19.07 to 2134. Io occultation and eclipse reappearance.

22/5 18.00 Callisto passing by Jupiter's pole.
22/5 18.35-18.54 Io transit & shadow egress
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  #6  
Old 19-05-2018, 09:04 AM
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Tinderboxsky (Steve)
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I have been wanting to view some of these recent and upcoming events. But! All of my gear I have with me for the recent South Pacific Star Party is securely packed at the bottom of all of our camping gear and is just too much trouble to unpack and then repack!

Shall have to be patient till I am back home in mid June.

We had two good nights at the SPSP. I completed Joe's Leo double star challenge on the first night - I still need to report on this. On the second night, I was swamped with visitors wanting to look through my scope. I did mange a look through some of the very big scopes at the usual favourites. They were just fantastic under such dark skies.

Quote:
Originally Posted by Tropo-Bob View Post
Io

Future events, which I will attempt to view:-
18/5 0.40 Ganymede occultation disappearance.
21/5 19.07 to 2134. Io occultation and eclipse reappearance.

22/5 18.00 Callisto passing by Jupiter's pole.
22/5 18.35-18.54 Io transit & shadow egress
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  #7  
Old 21-05-2018, 09:03 PM
Tropo-Bob (Bob)
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Io occultation & eclipse reappearance

Io
Using the Vixen ED 80mm (85x), I attempted to watch the cccultation of Io. Unfortunately, I lost Jupiter to the clouds a few minutes before the event. It did appear likely to disappear near the southern edge of the Southern Equatorial Belt (SEB).

I spotted Io reappearing at 21.32 to the side of Jupiter, adjacent to the southern edge of the SEB. Io was only about the width (from North to South) of the SEB away from Jupiter when it reappeared.

The Red Spot was also visible, being just past the halfway mark of its journey across the planet.


Future events, which I will attempt to view:-

22/5 18.00 Callisto passing by Jupiter's pole.
22/5 18.35-18.54 Io transit & shadow egress

28/5 18.45-20.46 Ganymede transit exit, shadow ingress & shadow egress.
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  #8  
Old 23-05-2018, 07:48 AM
Tropo-Bob (Bob)
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Callisto

Quote:
...I attempted an estimate of how far Callisto's orbital plane was north of Ganymede's. I thought about the same as the distance between the polar edges of the Equatorial Belts, or about 40% of the North-South diameter of Jupiter. I hope to test this by seeing Callisto pass Jupiter's South Pole by approximately this distance on the evening of 22nd May, at about 6pm. (Ganymede is only just inside Jupiter's disc at the pole when it passes, so Callistro should be approximately 35-40% of Jupiter's polar-diameter...
Callisto passed to the South of Jupiter last night at about 6-7pm, but clouds stopped me from seeing anything till about 9.15pm. by this time, Callisto had moved a little away from Jupiter. Nevertheless, looking at Callisto position, I estimated that it passed to the South of the planet by no more that 20% of Jupiter's polar-diameter. This is somewhat less than my previous estimate. (Used Vixen ED81mm with 85x (Yes, I keep calling this 80mm, but it is really 81mm).


Future events, which I will attempt to view:-
28/5 Ganymede transit and shadow events.
29/5 Io transit and shadow events.
30/5(around midnight) Callisto passes by Jupiter's northern pole.
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  #9  
Old 29-05-2018, 07:55 AM
Tropo-Bob (Bob)
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Ganymede Occultation & shadow events

Ganymede
Using the Vixen ED 80mm (85x), I viewed through very turbulent air the transit (NOT occultation) of Ganymede last night. I lost sight of it 6.48pm. It disappeared in the extreme northern part of Jupiter. Clouds prevented me from viewing Ganymede's reappearance.

I later viewed (125x) Ganymede's shadow, which traveled across Jupiter, just inside the planet's northern limb.

I had a final look at 8.05pm. Using 20x, it was a interesting view with both Ganymede & Io being together just to the edge of Jupiter. The bright star Alpha Libra with its attractively named companion, Zubenelgenubi, were also visible in the same field.


Future events, which I will attempt to view:-
29/5 Io transit and shadow events.
30/5(around midnight) Callisto passes by Jupiter's northern pole.

Last edited by Tropo-Bob; 30-05-2018 at 07:31 AM.
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  #10  
Old 29-05-2018, 08:45 AM
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Tinderboxsky (Steve)
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I am enjoying your reports Bob.
I am still travelling and won't be home till mid May.
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  #11  
Old 29-05-2018, 10:18 AM
Saturnine (Jeff)
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Managed to glimpse Ganymedes shadow transit last night but lots of high and middle level cloud spoilt the show. Skies cleared late in the evening but the seeing was very average making it difficult to image any detail.
Will hope to catch sight of Vesta in the next week, remember seeing it at last opposition when it was in Ophiuchus at mag. 6 .
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  #12  
Old 30-05-2018, 07:36 AM
Tropo-Bob (Bob)
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Io transist & shadow events

Io

I caught Io reappearing from transist at 8.19pm yesterday. Conditions were difficult being both cloudy and unstable air. Using the Vixen ED 81mm (85x), I did not see Io against Jupiter's disc at all before it reappeared.

Conditions had improved a little when I later viewed Io's shadow. The shadow appeared to fall just to the north of the NEB. Using 125x, I could not satisfactoraly determine if the shadow was really seperated from the NEB, so I changed scopes and viewed it again with my Tak FC100D. Using 148x. the shadow seemed seperated at first, but after a minute, the same doubts about being totally seperated re-emerged.


Future events, which I will attempt to view:-

30/5(around midnight) Callisto passes by Jupiter's northern pole.

1/6 & 2/6 The 'swing' of Io. Near stationary at the furtherest point of its orbit, I am hoping to see some movement in a North-South direction over a few hours as Io approaches or recedes from us in its inclinded orbital-plane. I hope this makes sense!

THANKS also to Steve & Jeff for your contributions to the thread.
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  #13  
Old 31-05-2018, 06:57 AM
Tropo-Bob (Bob)
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Callisto passes by North Pole

Callisto

I watched Jupiter over several hours last night with my Vixen 115mm ED (pictured below), as Callistro appoached Jupiter's North Pole. I ceased just after midnight, when Callistro was level with the Pole. I estimated that its distance from the limb was 1/6 to 1/5 (16 to 20%) the size of the Jupiter's North/South axis. The Great Red Spot was clearly visible at this time.

As an aside, I notice how seeing improved greatly after 11pm. Initially, I thought that this was because Jupiter was near the zenith, but a peep at the lower Saturn showed a much better view than I had of Jupiter at the same altitude. However, I had to dial the magnification down on the much lower Mars (about 35 degrees of altitude.) One of its pole caps appeared stikingly visible. (I haven't seen the cap this good for decades.)


Future events, which I will attempt to view:-

1/6 & 2/6 The 'swing' of Io. Near stationary at the furthermost point of its orbit, I am hoping to see some movement in a North-South direction over a few hours as Io approaches or recedes from us in its inclined orbital-plane. I hope this makes sense!
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  #14  
Old 31-05-2018, 09:20 AM
Saturnine (Jeff)
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Wanted to watch the Callisto approach to Jupiters limb last night but the weather here was unco-operative as usual. The sky was clear from late evening but wind gusts up to 50 kms / hr. and with wind chill factored in , the temp. was down to single figures. The temp was not a big problem, just have no protection from the S / SW wind direction.
Looking forward to August when on the 6th, 13th and 20th there will be double shadow transits of Io and Europa.
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  #15  
Old 03-06-2018, 07:57 PM
Tropo-Bob (Bob)
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Io's Swing & Europa's Shadow.

Io's Swing
I looked for this over several hours on June 1st, but did not notice any appreciable North or South movement when Io appeared to be near its furthermost point from Jupiter.

I did start to look for this on June 2nd, but was at a dark-sky site and become carried away with other awesome sights.


Europa's Shadow
The thin, North Temperate Belt seemed more prominent tonight and Europa's shadow seemed to fall directly upon it. (Used 100mm Tak at 105x.)


I have not yet planed to observe any more events.
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  #16  
Old 19-06-2018, 10:03 PM
Tropo-Bob (Bob)
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Europa's reappearance from eclipse.

Tonight, I attempted to estimate the length of time that Europa took to return to full brightness after it began to reappear on leaving Jupiter's shadow.

It is not an easy task to determine when the moon is back to its normal brilliance. I timed this from the first appearance of a speck of light. For the first two minutes, I could see Europa growing brighter in real time. After two minutes, I resorted to only looking at it every 30 seconds and determining if the Europa was brighter than 30 seconds ago. By this coarse measure, I estimated that it took 4minutes & 30 seconds for Europa to reach 100% illumination. I used my Iphone to time this, so looking at the bright screen also made this task more difficult.

My interest in timing this stems from the different orbits and sizes of the moons. Those moons with inner orbit should have a higher angler movement than the outer moons and thus should exit the shadow more quickly. I would expect Io to be quickest out and Callisto to be slowest. However, those moons with are somewhat larger, or smaller may slightly complicate this pattern.

Looking at future events, I may be also able to do timings of moons going into Jupiter's shadow.

I would also like to attempt to do a similar timing of the moons being occulted by Jupiter. My expectation is that the time for this should be similar to the length of time taken for the moon to reappear/disappear from shadow.

Future events that I will try and view:
June 20th: Io occulation disappearance.
June 22nd: Several events with Ganymeade.
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