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Jupiter / Uranus obs report

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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


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.


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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