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    Re: It Works.
    From: Arthur Pearson
    Date: 2002 Apr 8, 17:41 -0400

    Bruce et. al.
    
    Our digression into SHA meridian was not time wasted; I have finally
    grasped the concept. Although we may conclude that given Bill Noyce's
    insight, the method is unnecessary, I think it is remarkably elegant
    solution.  As I now understand it, LAN is essentially used as a way to
    mark our place on the SHA scale without regard to exact time or
    longitude.  The SHA Sun simply does not vary much over an hour (about
    3.4' in the hour I looked at), so this is pretty accurate even without
    exact time.  Convert to arc the time from LAN to the lunar to we can get
    SHA meridian at the time of observation within +- 3' roughly. That's
    pretty good for a vessel with a chronometer that may be out by 30
    minutes or more.  It is as if one re-set the "SHA Clock" each day using
    LAN.  A very elegant derivation, I can't help but think there are other
    uses for the principle.
    
    That said, I am relieved by Bill's insight that if we are using
    celestial fixes to begin with, the error in time and longitude will
    cancel out. It eliminates the need for special procedures in
    anticipation of a lunar.  I need to work out the example to make sure I
    understand it, but it does feel we have come full circle.
    
    Regards,
    Arthur
    
    -----Original Message-----
    From: Navigation Mailing List
    [mailto:NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM] On Behalf Of Bruce Stark
    Sent: Monday, April 08, 2002 2:42 PM
    To: NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM
    Subject: Re: It Works.
    
    Like George, I've been "Off watch." But for longer time and for less
    interesting reasons, one of them being that a backhoe took out our
    telephone
    line.
    
    A lot of good postings. William Noyce's insight, that the problem we
    were
    discussing on the "It Works" thread takes care of itself, is beautiful.
    Why
    didn't we see that?!
    
    I'm sorry now I posted that method of finding SHA meridian, etc. It
    injects
    the old nautical astronomer's way of thinking into the discussion. It
    isn't
    needed, and confuses the issue. Arthur and others should forget about
    SHA
    meridian and put to practice what William has said. That way they will
    see
    how it works and develop confidence.
    
    Don't think I have anything to add to what George has said. Glad he
    pointed
    out that noon is the worst time to get local time.
    
    Hope the "Artificial Horizon" thread will remain as lively.
    
    Bruce
    
    
    

       
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