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    Re: 18 june 2013 lunar distance
    From: Frank Reed
    Date: 2013 Jul 1, 15:05 -0700

    Dave, you wrote:
    "true xld= in deg +106 deg 34' 28.466124" "

    Seeing as it's summer movie season, and the fish are biting, I shall paraphrase the original summer blockbuster about biting fish: "You're gonna need a bigger vernier...!"

    Note that differences smaller than 1 or 2" in lunars are meaningless since the Moon is so lumpy. Unless you build a model that accounts for the flat parts and the high parts and then correctly calculates the librations which rotate those points onto the limb in the appropriate direction to the other body, then you're calculating purely academic numbers. To put some of these numbers in perspective, the distance to the Moon just happens to be a bit more than 200,000 nautical miles on average. the conversion between angles as ratios to seconds of arc also happens to be just over 200,000 (it's 3438*60). So that means that a 1 second of arc difference in a measured angle at the Moon's distance corresponds to a change in the location of the Moon's center or equivalently a change in the the altitude of mountains of other features on the Moon's limb of just about one nautical mile. And for fun, that last digit in the angle that you've quoted, a millionth of a second of arc, is equivalent to a shift of 2 millimeters in the height of the Moon's limb. A grain of moondust! :)


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