Amazing Io shadow transit - anyone else see it?

[RobertI]

The clouds cleared and consulting Sky Safari, I saw that a shadow transit of Io was just starting. Five minutes later I had the 102ED with binoviewers set up at around 170x. The seeing was awful with Jupiter ‘boiling’ but the shadow of Io was perfectly clear, a tiny black disc which seemed totally unmoving as the other moons danced around. Io itself was really close to the limb of Jupiter and over the next few minutes I watched it touch the limb and then start to move across the face of the planet. What amazed me most was that, because it was moving along one of the dark equatorial belts, it was visible as a tiny bright disc, and was visible for a good ten minutes until it finally disappeared against the disc of Jupiter. Quite an experience. 🙂 Anyone else see it?

Edited September 10, 2022 by RobertI

[rojay]

Hi, yes I saw it too, very cool. Thanks for the report, great description.

[Froeng]

Yes! Just came in. Unfortunately I did not see Io touching the limb as Jupiter was moving behind the roof of the house! But the shadow appearing on Jupiter and moving across it looked amazing. As if someone punched a hole into Jupiter…

saw it in my C8, with binoviewers and a pair of 9mm Vixen LVs, at 225x. Jupiter is enormous at the moment!

Good night… 

[NGC 1502]

Yes I was out too, nice and clear at Southend in Essex.

At 23.06 BST Io’s shadow was a notch out of Jupiter’s limb, after a few minutes the shadow was an inky black dot fully on Jupiter’s disc. I watched as Io itself crept ever closer to Jupiter.

At 23.29 Io appeared as a “pimple” attached to Jupiter’s limb😊. By 23.34 the bright dot of Io was fully on Jupiter’s disc.

As the minutes ticked by Io became progressively harder to see as it moved further from the limb darkening. By 23.50 I could no longer discern Io, but the shadow remained easy to see.

Instrument- Hinds 6” Dob, 6mm Radian = 150x.

A lovely clear night at this sad time.

Ed.

[Stu]

Excellent report @RobertI, glad you managed to see that. I wasn’t out last night, but do want to start catching some of these events.

I’ve always found Io and Europa to appear as bright disks when they first appear against the limb darkening, but they then become increasingly hard to see until they disappear, only reappearing near the other limb.

Shadow transits to me have always been possible to see right the way across, but you did say the seeing was poor so perhaps that’s why you lost it?

The ones to look out for are the rarer transits of Callisto and Ganymede. They orbit further out and more slowly, so they transit less frequently. The number of observable transits is actually pretty small, but well worth looking out for. That’s because they have a lower albedo than the other two and appear dark against Jupiter’s bright disk. You can track them right across. I once recall viewing a double shadow and then seeing what I thought was a third shadow. This turned out to be Callisto. On careful observation you could tell the difference as it wasn’t quite as inky black as the shadows and was softer around the edges, while the shadows are razor sharp.

The other effect to watch for as opposition approaches is that the shadows get closer to the moons, and at opposition actually the moons are overlapping the shadows. Makes sense as the Sun is behind us, with Jupiter opposite it in the sky so everything lines up nearly perfectly.

Sorry for rambling on!! 😜

[RobertI]

6 minutes ago, Stu said:

Excellent report @RobertI, glad you managed to see that. I wasn’t out last night, but do want to start catching some of these events.

I’ve always found Io and Europa to appear as bright disks when they first appear against the limb darkening, but they then become increasingly hard to see until they disappear, only reappearing near the other limb.

Cheers Stu, I’ve only observed a couple shadow transits and being able to the see the moon’s bright disc on the planet was something new. Interesting to hear that what I saw is common for Europa and Io.

11 minutes ago, Stu said:

Shadow transits to me have always been possible to see right the way across, but you did say the seeing was poor so perhaps that’s why you lost it?

I think my description was confusing (I’ve now removed the offending sentence), I did manage to see the shadow across the whole disc!

13 minutes ago, Stu said:

The ones to look out for are the rarer transits of Callisto and Ganymede. They orbit further out and more slowly, so they transit less frequently. The number of observable transits is actually pretty small, but well worth looking out for. That’s because they have a lower albedo than the other two and appear dark against Jupiter’s bright disk. You can track them right across. I once recall viewing a double shadow and then seeing what I thought was a third shadow. This turned out to be Callisto. On careful observation you could tell the difference as it wasn’t quite as inky black as the shadows and was softer around the edges, while the shadows are razor sharp.

The other effect to watch for as opposition approaches is that the shadows get closer to the moons, and at opposition actually the moons are overlapping the shadows. Makes sense as the Sun is behind us, with Jupiter opposite it in the sky so everything lines up nearly perfectly.

Fascinating, I have a lot to look forward to with these transits over the coming months. I need keep a close eye on what’s happening. 👍

15 minutes ago, Stu said:

Sorry for rambling on!! 😜

Ditto. 😆

[RobertI]

7 hours ago, NGC 1502 said:

At 23.29 Io appeared as a “pimple” attached to Jupiter’s limb😊. By 23.34 the bright dot of Io was fully on Jupiter’s disc.

As the minutes ticked by Io became progressively harder to see as it moved further from the limb darkening. By 23.50 I could no longer discern Io, but the shadow remained easy to see.

Pretty much exactly what I saw! 

[stuy]

Yes a lovely transit sadly the seeing is as around 5/10  as stated booking with a tail end of the jet stream playing havoc ! Nice to see the yellowish disc against the planet some nice fleeting glances of 3 ovals too 

[Zermelo]

I saw the shadow around 23.45, very nice. I couldn't make out Io itself.

I found Jupiter itself a bit underwhelming and a mushy, though the shadow was very tight and sharp. It could have been seeing as you say, although I managed well with doubles earlier on.

[Pixies]

On Sun 25 Sept (the day before opposition), there's a transit of Io - where the moon itself is only 2 minutes behind the shadow.

Sun 25th
21:24 BST, Io's shadow begins to cross Jupiter.
21:26 BST, Io begins transit of Jupiter.
23:38 BST, Io's shadow leaves Jupiter's disk.
23:40 BST, Io ends transit of Jupiter.

I'm not sure how close they will appear at that separation, though.

 

NOTE: I'VE EDITED MY ORIGINAL POST WITH CORRECT TIMES (SEE BELOW)

 

Edited September 16, 2022 by Pixies

[Stu]

48 minutes ago, Pixies said:

On Sun 25 Sept (the day before opposition), there's a transit of Io - where the moon itself is only 2 minutes behind the shadow.

Sun 25th
20:24 BST, Io's shadow begins to cross Jupiter.
20:26 BST, Io begins transit of Jupiter.
22:38 BST, Io's shadow leaves Jupiter's disk.
22:40 BST, Io ends transit of Jupiter.

I'm not sure how close they will appear at that separation, though.

 

Looks like the moon may just eclipse the shadow a little which will be good to see.

Are you sure on timings? SkySafari says 9.23pm for the first contact.

[Laurieast]

Stellarium

S&T Lists

Sunday, September 25, 2022

01:28 UT, Io exits occultation behind Jupiter.
20:24 UT, Io's shadow begins to cross Jupiter.
20:26 UT, Io begins transit of Jupiter.
22:38 UT, Io's shadow leaves Jupiter's disk.
22:40 UT, Io ends transit of Jupiter.

Edited September 10, 2022 by Laurieast

[Pixies]

Ah apologies. Looks like I've put down times in UTC. 🤪

I used S&T. However, I was certain I converted it to BST. Perhaps I found an old text file where I had put 'BST' but not converted the actual times. 

[Laurieast]

There's still a three minute difference somewhere with Io first contact?

 

[RobertI]

Will definitely put that one in the diary. 

[lvan]

I saw this. Initially thought it was a spec in my ep so swapped it out!

[markse68]

There’s one tonight/Sat morning (starts 1am) complete with GRS, and the forecast is clear 😃 

 

[RobertI]

On 16/09/2022 at 09:43, markse68 said:

There’s one tonight/Sat morning (starts 1am) complete with GRS, and the forecast is clear 😃 

 

A crying shame, it was clear but I am laid low with a cold and was just too tired. 🙁 Hope everyone else enjoyed it. 🙂

[Froeng]

I hope you feel better! It was indeed enjoyable, especially after the initially crap seeing, which steadied later in the night...

[Nigella Bryant]

I captured Io in transit on the 17th September

[Froeng]

Looks good. It looks like a natural eyepiece view! Is that a single frame? What is your setup?

[Nigella Bryant]

39 minutes ago, Froeng said:

Looks good. It looks like a natural eyepiece view! Is that a single frame? What is your setup?

No, 9,000 frames and a 25% stack. C11, Zwo Asi 224mc camera and 2.5x powermate. Imaging @ f25. 

[Orlando Gonzalez]

So cloudy I can barely see the moon! Would have been nice.