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Old 26-09-2010, 10:54 AM
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Observing report 25/9/10

After 9 million consequetive cloudy milleniums, it finally cleared on what looked like a very unlikely day. Late a'noon around sunset, some storm clouds rolled in and to the non-initiated, it would have been a write off. But checking the satpic loops it showed that it would clear.

So I set up the scope for a Jupiter and Youranus session. After the massive absence, I've learned a few things:

A. I forgot how to use the scope
B. A cable which connects the jumpstarter to the scope is apparently no longer in this universe, hence I was unable to run the fans and heaters.

After trouble shooting point A, I was on me way.

Collimation was atleast striaght forward and was done in 2 miutes. One of the strongest features of an SDM imo is how easy collimation is. After years of messing around with tools and non-intiuative designs, it's like walking out of a Darwin summer into an air conditioned room.

Time: 8pm-1045pm
Scope: 12" F/4.4 dob
Seeing: 1/10-5/10
Transparency: 2/5
Dew: Light

JUPITER

About 8:30pm, caught a shadow transit of Ganymede. Seeing terrible, boiling at 166x so not much detail could be seen. I also had no fans running, so the delta temp was up to 4C, and defocusing the planet your could see the thermals on the mirror.

For the next several minutes Ganymede itself was emerging from the preceeding limb of Jupiter, it was cool seeing half of the moon infront of the planet and the other half beyond it. The disk appeared white against the planet.

Over the next hour or so, I could gradually increase the mag as the mirror and air temps ever so slowly closed the gap, eventually topping out at 256x. However the view at 204x was pretty nice. Lots of detail seen. Two thread-like dark barges were spotted in the nothern temperate belt, as was an elongated white feature in the northern temperate zone.

A long dark filament was seen hanging from the NEB into the EQ zone. THe SEB was faintly visible, moreso than the last time I saw it. I was going to sketch Jupiter but was clouded out half way through, only for it to clear right after I packed everything in.

URANUS

Not much to see really, at times I could get a fairly sharp focus at 308x. I could see that the planet is not a perfect sphere, but oblate....otherwise nothing of note. I was hoping to catch some albedo features as some other observers have, but seeing was too unstable.


------------------

Some passing clouds also provided an opportunity to test a long running theory of whether or not thin clouds improve seeing and details seen on an object. It seems to me, on this night anyway, that clouds actually destablise seeing, but can act as a natural filter cutting glare. This has the illusion of cleaning up the image, but you don't actually see any addtional detail. The reduced glare simply means that imperfections or light scattering in your eye/optics etc are far less obvious.
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Old 26-09-2010, 12:04 PM
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Nice Report,

I observed jupiter and managed to see the transit of Ganymede aswell.
Although you mention seeing it as white disc against jupiter where i saw it as a black dot at 138x magnification.

I saw Uranus the other week it was my first time, featureless but pretty.

regards orestis
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Old 26-09-2010, 12:08 PM
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Quote:
Originally Posted by orestis View Post
Nice Report,

I observed jupiter and managed to see the transit of Ganymede aswell.
Although you mention seeing it as white disc against jupiter where i saw it as a black dot at 138x magnification.

I saw Uranus the other week it was my first time, featureless but pretty.

regards orestis

Not referring to the shadow, but rather the actual moon was emerging from infront of Jupiter. The moon itself appeared white against the planet's disk. So a pretty cool event

cheers
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Old 26-09-2010, 12:40 PM
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Paddy (Patrick)
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Good to hear that you finally got a chance to do some observing and that you had a better night than I did. I had about 5 minutes between collimating and cloud cover. Catching those transits is always a joy and sounds like you saw some good detail. I agree about thin cloud cover giving the illusion of cleaning up the image.

Hope you find your cable.
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Old 26-09-2010, 09:51 PM
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Originally Posted by Paddy View Post
Good to hear that you finally got a chance to do some observing and that you had a better night than I did. I had about 5 minutes between collimating and cloud cover. Catching those transits is always a joy and sounds like you saw some good detail. I agree about thin cloud cover giving the illusion of cleaning up the image.
Been a long time coming, was nice to do what I enjoy most once again. It's quite amazing the detail on Jupiter in sub-good seeing, compared to the typical supersonic jetstream. It's fun watching all those white ovals, cloud bands, barges and curdled detail snap into focus! Seeing last night was generally very sub-ordinary, defocusing the planet slightly one could watch in awe at the "violence" of the air rushing past. I'd love to see it in genuinely good seeing.

Quote:
Hope you find your cable.
Don't think so, can't find the bloody thing anywhere. Come to think of it, my brother came and took some of his stuff away from his former room, where my gear is now stored....and may have took the cable with him....
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