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    Lunar Distances v. Meridian Angles
    From: Chuck Griffiths
    Date: 2002 Feb 26, 13:07 -0500

    OK, I know George H. promised he'd cover using moon altitudes in place of lunar
    distances in his next part but I'm going to go ahead and jump the gun by asking
    a question. Now that George has helped me start to understand lunar distances I
    can't help but consider an alternative approach to finding GMT. Why can't we
    observe the altitude of the moon and one other body and, using our assumed
    latitude, solve for  the meridian angle of both bodies. The difference between
    the two angles should change by the rate at which the moon moves through the sky
    faster than another body. If that's true, can't we find the meridian angle
    between the two bodies for the even hours, say on either side of what time we
    think it is, and use the same inverse linear interpolation approach to find the
    time of our sight?
    Of course, I can think of a couple issues with this approach worth discussion.
    First, this only works when the altitude of the moon and the other body change
    reasonably with time, i.e., we can't do it when either body is close to being a
    meridian sight. Second, we need both altitudes simultaneously. I think this
    could be solved by alternately observing one body then the other several times
    and graphing the sights so that we could derive an averaged simultaneous
    altitude from the graph.
    Lastly, why bother when the other methods thus far described work? It seems to
    me that if this is a workable solution it provides a method of checking time
    using techniques that are already in most navigator's "bag of tricks". That is,
    we get to correct for refraction, horizontal parallax, augmentation, etc. using
    the tabular methods we use for other sights.
    Chuck Griffiths
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