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Jupiter on Feb 7 under very good seeing

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#1 Eddgie



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Posted 08 February 2013 - 10:58 AM

Seeing was not perfect, but one arc second in frequent 30 second stretches.

I observerd using my C14 and binoviewers for a session that stretched over about 3 hours with an hour break for dinner.

The most frustrating thing was that it was gusty and at 300x, the scope would keep shaking, though my best observations were generally at less than 267x.

And what a spectacular view. Rather than describe it in detail, I am referencing a picture taken with a C8 that shows about the level of detail I was seeing visually in case people want to know what kind of detail I usually see visually on a night of good seeing. This picture pretty much nails it in terms of detail:
CN Forum image from 2/7

In particular the eddy structure following the GRS shows with a bit more conrast visually with the two big egg shaped swirls being a bit more defined in the C14 at 267x. At 305x, I felt that they dimmness made it harder to see the graduation of the shading at the bottoms of these features, but at 267x, they were very apparent.

Also the big festoon above the GRS seemed more linked to the one to the right of it by the big wisker arc when viewed visually. I suppose this is because of the better contrast of the C14.

Of course everything looked a bit sharper in the C14, but that is a fucntion of scale.

It was fantastic though. I wish it had not been so gusty.

Ganymede was showing a distinct abbedo brightening right at the meridian, and I thought I could see a very slight brightening where Osiris should have been based on my simulation, but it just wasn't steady enough to be sure, and I was focusing more of my attention on Jupiter itself.

Io was featureless initially, but pale yellow. About 8:45m ut started to ingress the limb just below center of the SEB. At this point, it did start to appear slightly shaded at the north and south. It really jumped out from the planet behind it too. Binoviewer illusion no doubt, but so profoundly 3D. Once again, too gusty at 305x to really study it, but seeing was good enough that I think it would have been one of those rare nights where I might have been able to resolve a bit more had the seeing cooperated.

I am attaching my simulation image of an enlarged Ganymede to show the features that were in view, then a shrunken one to kind of give the idea of how it looked in the eyepeice. You can see that the features are very bright and should be visible, and they were indeed, but only just barely detectable (but then so much of it is just barely detectable, eh? Isn't that why we do it??). Anyway, the big picture on the left shows what was facing, and the smaller image shows about how it appears at the eyepice. I am sure it would have been a bit better at 305x, but things just would not stay still. You can see though that these features do still show even at 265x. At least this is about how they looked to me.

Anyway, Just shorth of excellen seeing, but gusty. Still, a very satisfying night. One of the best in a month and the GRS eddy complex is simply amazing. There really isn't any other way to describe it.

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#2 Eddgie



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Posted 08 February 2013 - 11:03 AM

Just a quick followup. I did not observe the bright cap-like feature on the right limb of Ganymede. I saw the bright area at the center, and the almost barely barely visible Osiris, but only barely and only once. But the center bright area did show a couple of times. It has quite a bit of contrast because of the mare to the right side.

If you look at the smaller image on the right though, that kind of shows how difficult these things are to see. I have seen detail more clearly on Ganymede though, but not last night. A lot has to do with how it is positioned. That is why I always check my observations using Starry Night Pro after the session. I want to know what should have been there so I can see if my visual observation was indeed accurat and not just wishful thinking.. LOL.

#3 REC


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Posted 09 February 2013 - 01:35 PM

Great report! If you where seeing detail like this picture and in a BV, it must have been breathtaking.

I see we are going to have a shadow transit for a while at 7pm. EST, so hope seeing id good:)


#4 Eddgie



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Posted 09 February 2013 - 01:44 PM

I need to clarify something. In my post, I explained that the picture shows the level of detail I could see.

But Jupiter doesn't look like it does in the picture. First, colors are not as pronounced, and second, the contrast of many of the features is not quite as high, though for some details it is perhaps a bit higher.

Pictures do tend to show color with far more saturation because of the nature of imageing and the ability to use sensitive detectors and give them a lot of light though hundreds of exposures.

I could see pretty much all of the detail presented in the picture, but once again, Jupiter doesn't look like that at the eyepeice. It looks much less colorful (though I do indeed see color and lots of it) and more subdued.

But the level of detial is about the same. I don't think there is anything in this picture above that I could not see.

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