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Jupiter at 03:00 today. Excellent seeing

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Jupiter at 03:00 today. Excellent seeing

Posted by Paul A Brierley at 11:57 on 2010 Aug 06

This morning at 02:45 I arose after a very restless sleep to find to my surprise a partly clearing sky, with Jupiter high in the south.I dressed, and went out side and began observing Jupiter, through my 10" f4.8 OD250s. The view's were stunning at all magnification's, with x200 probably being the best magnification (Vixen LV 6mm) seeing was ANT2 or better with a little haze.After twenty minutes glued to the eyepiece, I started to see detail in the planets cloud belts. The NEB looked particularly dark and brown, with what I at first thought was the Red spot. I soon realised that it wasn't, because the SEB which is still invisible, is above the NEB in my Newtonian reflector. Did anybody else notice a small oval that was visible in the NEB?Through my 10" and the 6mm LV, the oval would have been towards the east of the NEB with a tiny, dark spot in the centre.I am sure that there is a very simple explanation for this, and I would suggest that what I actually saw, was a white oval, with the shadow of a Moon in transit? All the Galilean moon's were lined up to the right. And i think it might have been the shadow off Io, but I can not sure. If anybody was looking or imaging Jupiter this morning, and saw this. Could you please tell me what I saw.If I had been more prepared, I would have made an observation sketch. Next time I will. I didn't realise the bright star visible towards Jupiter's left (west?) was Uranus. I'll know next time what to look out for.

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Re: Jupiter at 03:00 today. Excellent seeing

Posted by David Arditti at 16:22 on 2010 Aug 06

Paul, according to WinJUPOS software, at the time you give, there were no satellite shadows on the disk. It would have been obvious if there had been anyway. Satellite shadows are quite large and intensely black, easily recognisable when you see one.The NEB currently contains both white ovals and dark brick-red spots. Longitude of the central meridian at the time you report is about 19 deg. (System II)A map made by Einaga on August 01 shows a dark spot in the NEB at II=85 and a white oval at II=100. Both of these would be, as you describe, to the East of the CM (following) at the time you give, so you could be referring to either of them, but it seems you are talking about the dark red spot.

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Re: Jupiter at 03:00 today. Excellent seeing

Posted by Paul A Brierley at 21:06 on 2010 Aug 06

Thanks David,I thought it had to be something simple. It was nice to go out on the fly, and set UP. It's one of the advantages of a dobsonian, there isn't any messing about.If it's clear again tomorrow, then I will go out again.