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    Re: Chronometer Suggestions
    From: R B Emerson
    Date: 2009 Jan 6, 07:12 -0800

    Yewbetcha!  At the equator, every minute of error is one nautical mile
    and that makes a second's error about 100 feet.  Given that a really
    good round of sights at sea might be good to a mile or two, where's
    the problem?  The problem is that these errors can become cumulative.
    And even if they're not, navigation is all about accuracy; if timing's
    sloppy, what else might be sloppy, too?  Sooner or later, the boat is
    put at risk because of all the slop.  Not Good.
    (Why "at the equator"? Because the higher the latitude, the smaller
    the distance covered by a degree of circumference.  The nautical mile
    is derived from the Earth's circumference at the equator divided by
    360 degrees.  Measure the Earth's circumference at, say, 45N, and the
    number of miles is less but there are still 360 degrees to that
    circumferential circle.)
    On Jan 6, 8:05�am, William Sellar  wrote:
    > As a beginning celestial navigator, I am wondering how much time and watch 
    accuracy is actually required for practical navigation.� Can we predict how 
    many miles off one would be for every second of time error?
    > �
    > Bill
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