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    Re: Ephemerides at Columbus' Time
    From: Craig Levin
    Date: 2012 Oct 25, 10:51 -0700

    John:

    I'm putting together a planetarium show on Tycho Brahe that should be ready in the spring. Kepler worked with Brahe when Brahe was in Prague, in the last years of his life. Were it not for Brahe, Kepler wouldn't have had pages & pages of observations of Mars to allow him to derive his 3 laws of planetary motion.

    The situation before Brahe's work was pretty sad. Many astronomical constants hadn't been checked for their accuracy since the days of the Greeks. Brahe's table for refraction was one of the first that came close to accuracy. If I might venture a guess about why Columbus & other early explorers had such a sad record in celestial navigation, it's as much a result of inaccurate work by the writers of the ephemerises as anything else. For instance, a predicted conjunction of Jupiter & Saturn was days off from the actual event. Even the position of the Sun wasn't always accurate.

    Craig

    > Brad -
    >
    > Yes indeed....honest to god ephemerides produced by Regiomontanus,
    > Copernicus, and Kepler. He even has some teaching texts with marginal
    > notes in Copernicus's handwriting. Yes, he even lets me touch them.
    >
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