Friday, October 21, 2011


Had a look at Jupiter in my 13" during the Live Oak school star party. The south equatorial belt that was missing last year is back--somehow I had forgotten about the disappearance and hence didn't really notice that it had reappeared.

I was surprised to see a very dark spot a little bit east of center on the north equatorial belt at JD 2455856.5754. It looked a little fuzzier than a moon shadow, and possibly slightly elliptical. It moved in the same direction as Jupiter was rotating. Experimenting with my collection of gel filters showed that the spot got much harder to see through a magenta filter. Vivid pink, red and orange also decreased contrast. Green may have enhanced contrast slightly. I hypothesize that the spot was dark red in color.

I also saw the Great "Red" Spot--in the words of a colleague, it looked like an empty area.

Both the dark spot and the Great Red Spot looked very good in my colleague's 8" F/6 with a binoviewer.

Update: I looked on Cloudy Nights. The dark spot is nicely seen here. I am pleased to note that I got the color and shape right with my filter swapping technique: it's definitely dark red and oval in the photo. These spots are apparently known as "barges". More information and links here.

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