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Walking on the Moon

Chasing A Shadow, Then A Pimple!


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9.40pm, clear, still, mild - 8SE set up ready - spotted Jupiter, and away we go!

Aligned on Jupiter.  Ganymede, Callisto, and Io easily seen, but Europa was in transit, and was not to be seen, neither was its shadow.  For nearly 2 hours, I played about with magnification and the Neodymium filter, but still nothing.  The finally, at 11.20, I spotted Europa's shadow in AV, to the NE of Jupiter's face.  The moon itself was to the NW.  Mag, x113; filter made little difference.

20 minutes later, Europa appeared as a tiny pimple as it emerged from Jupiter's disc to the NW.  Splendid results after 2 hours of patience!

Still not ready to pack up, I then went for M5, the Rose Cluster, a glob in Serpens - a dense bright core, with many peripheral stars discernible at x113.  In the same FOV at x56 was the double 5 Ser, 11.4", the components looking close at that mag, with the faint companion clearly seen.  Then:

M10, GC, Ophiuchus - many individual stars seen at the periphery, x102.

Finally, M12, GC, Ophiuchus - similar size and magnitude to M10 - a fuzz in a distinctive starfield (three bright NS pairs to east) - again, more peripheral stars detected at x102, then lots of clear component stars x145.

I took one last look at Jupiter, with Europa then well clear of the disc, and finished at 12.30.  Almost three hours of pleasure, and patience rewarded!

Doug.

 

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Excellent report Doug,

I also was out observing and imaging the Europa transit for the best part of 3 hours. Seeing was very good in patches, so I was able to see some lovely blue festoons in the NEB, with the GRS putting in an apearance towards the end ?

Cheers, Geof

 

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Glad your perseverance paid off in the end Doug. It sounds like your seeing conditions were perhaps not the best? Having said that, the shadow Transit didn’t start until 10.44 and the shadow itself was rather small compared with that cast by Io so it was certainly a trickier target.

I could not pick up Europa over the surface and had to pack away before it got towards the limb where it might have been more obvious.

Thanks for the report :) 

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2 hours ago, Stu said:

Glad your perseverance paid off in the end Doug. It sounds like your seeing conditions were perhaps not the best? Having said that, the shadow Transit didn’t start until 10.44 and the shadow itself was rather small compared with that cast by Io so it was certainly a trickier target.

I could not pick up Europa over the surface and had to pack away before it got towards the limb where it might have been more obvious.

Thanks for the report :) 

Thanks Stu.  I'm kicking myself now, 'cos I was so intent on seeing more of Europa's shadow that I failed to linger on the moon itself and watch the "pimple" separate out from the planet!

Doug.

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3 hours ago, Stu said:

I could not pick up Europa over the surface and had to pack away before it got towards the limb where it might have been more obvious.

Referencing your comments in the other Jupiter thread, that certainly was the case Stu. I couldn’t discern the moon during it’s transit until it reached the limb. It was detectable, on and off, for about the last 5 to 10 minutes before it started to emerge...

That was in the 120 at 134x

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1 hour ago, cloudsweeper said:

Thanks Stu.  I'm kicking myself now, 'cos I was so intent on seeing more of Europa's shadow that I failed to linger on the moon itself and watch the "pimple" separate out from the planet!

Doug.

Yes, it’s tricky to know what to look for sometimes. Easy to get fixated on one thing and forget somethe else more interesting. Unfortunately I got clouded out before Europe became visible.

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6 minutes ago, Stargazer McCabe said:

Referencing your comments in the other Jupiter thread, that certainly was the case Stu. I couldn’t discern the moon during it’s transit until it reached the limb. It was detectable, on and off, for about the last 5 to 10 minutes before it started to emerge...

That was in the 120 at 134x

That makes sense and matches my previous experiences. Only on rare occasions have I picked up one of the bright moons whilst over the surface and away from the limb.

I think it is Callisto and perhaps Ganymede, the two moons which transit much less frequently than Io and Europa due to their longer orbits, which are darker and appear more like a shadow transits than a moon transit, it’s easy to mix them up but it is also possible to follow them across the dull transit on the rare occasions the timing is favourable.

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Good report Doug :smiley:

With my ED120 I could see Europa against the disk of Jupiter during the early and late parts of it's transit but lost it as it crossed the central part of the disk. I've noticed this before with transits and I put it down to the limb darkening effect making the moons disk easier to spot when it's close to a limb but much harder in the central area.

Europa's shadow was much easier to spot and track right across the disk.

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@Stu a while back we observed an Io shadow transit, which seemed a bit larger than last night’s. Again, we picked the moon up at the beginning and the end only.

Haven’t even witnessed a shadow transit of the other two yet. But will remember your suggestions if we do and it coincides with a clear evening...

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2 hours ago, Stargazer McCabe said:

@Stu a while back we observed an Io shadow transit, which seemed a bit larger than last night’s. Again, we picked the moon up at the beginning and the end only.

Haven’t even witnessed a shadow transit of the other two yet. But will remember your suggestions if we do and it coincides with a clear evening...

I think that the Io shadow is bigger because it orbits closer to Jupiter so casts a bigger shadow.

The Callisto events are more rare, I’ll try to flag some in the heads up forum. I remember a while back there was a triple shadow transit and a Callisto moon transit and it looked like a fourth shadow (I think I remember that correctly!!) seeing was very poor but I did just about see it.

EDIT My apologies, my memory failed me, it was a double shadow transit with a Callisto transit that also looked like a shadow, just a bit less intensely black.

SECOND EDIT Sorry, it was Ganymede not Callisto!! DOH!

 

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