Ganymede transit Thursday night

From: David Kingsley (kingsley@No-Spam)
Date: Fri Feb 28 2003 - 02:55:27 MST

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    > Michelle wrote: Seeing is good.
    >Transparency excellent. The planets tonight were stunning.

    Did you happen to catch the Ganymede transit tonight on Jupiter? I
    had the 7 inch Starmaster Oak Classic in the backyard near Stanford,
    and we had some of the steadiest seeing I have seen locally in weeks.
    Ganymede was obviously dark against the surface of Jupiter when near
    the middle of the planet around 9:15 pm , but then got hard to see as
    it approached the limb, and finally turned to a whitish dot
    superimposed on the limb of Jupiter just before emerging from the
    planet around 10:30 pm. A great example of limb darkening on Jupiter!
    (Io and Europa are normally harder to see when in the middle of the
    planet than at the edge. Ganymede has a darker surface and showed
    the opposite pattern). The GRS was perfectly placed near the
    meridian during much of the transit, behind Ganymede itself, but
    preceding Ganymede's shadow. The shadow was bigger, darker, and
    sharper edged than the moon itself, and the two dark spots made a
    great set of brackets for the pinkish GRS. Just after Ganymede
    emerged from Jupiter, it made a beautiful tight double star with
    Callisto. Minutes later, Callisto went into eclipse behind Jjupiter,
    as Ganymede was moving further away. Humidity was high but the
    views were often rock steady for minutes at a time. Hope the good
    viewing continues into the weekend both at Plettstone and at sites in
    the Bay Area.

    David Kingsley



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