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    Re: Jack Aubrey's fixing of longitude
    From: Frank Reed
    Date: 2011 Jun 20, 15:13 -0700

    Dave W, you wrote:
    "On 3 Jan 1818 at 21:50:57, it looks like Venus transited Jupiter, a truly once in several lifetimes occurrence."

    Yeah, wouldn't that have been amazing to see... Unfortunately for the history of astronomy, because this happened only about 30 degrees from the Sun and in the southernmost part of the ecliptic, the best viewing locations were in the South Pacific in an era when there weren't many astronomers in that part of the world. You can simulate this in Stellarium, too, and it looks like Venus occulted Callisto (or "satellite IV" as it was universally known back then) before transiting Jupiter and Io (satellite I) after transiting. There's a diagram simulating the transit on the Wikipedia "Occultations" page which Peter H. called to our attention last month. They don't really do it justice though since Venus has a higher albedo than Jupiter and of course it's much closer to the Sun. Venus would have looked more like a big white hole on the face of Jupiter with a slender dark crescent on its trailing edge.


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