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    Re: Lunar by altitudes
    From: Dan Allen
    Date: 2002 Feb 26, 18:47 -0800

    Welcome to the list!
    I assume that you are the same Bruce Stark that is the author of the book
    about lunars that some of us have?  Many of us have been hoping to
    find out more of the technical details behind your lunar tables, since
    there is not a lot of explanation in the book about the underlying
    algorithms, etc.
    Anything you could share on these topics would be appreciated by the
    Dan Allen
    -----Original Message-----
    From: Navigation Mailing List
    [mailto:NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM]On Behalf Of Bruce Stark
    Sent: Tuesday, February 26, 2002 12:12 PM
    Subject: Lunar by altitudes
    I just got signed on to the List, and probably shouldn't jump in so soon.
    The idea of comparing the altitude of the moon with that of one or more other
    bodies to get Greenwich time has been around almost continually for at least
    two centuries. It's such an appealing idea that many of the best navigation
    authorities have been blind-sided by it.
    First: Consider what you know about the reliable accuracy of altitudes taken
    from the sea horizon, especially from a small boat. You will be combining the
    errors of several such altitudes.
    Second: Consider what it is you are trying to do. You are trying to measure
    the moon's position in her orbit, NOT the rotation of the earth. If your
    latitude is less than 30� there may be times when you'll actually see the
    moon when her orbital motion is perpendicular to the horizon. At higher
    latitudes, never.
    The moon's is always within about 5� of the ecliptic. Her enlightened limb
    points to the sun and shows the path of her orbit. How often do you see the
    moon when her horns are pointing straight up or straight down?
    Bruce Stark

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