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    Re: The Noon Fix
    From: Ralph Clampitt
    Date: 2009 Apr 8, 13:49 -0800

    Just like to add, as a list follower, that this kind of thread is of
    great interest to those amateurs among us.  I will be crewing for my
    son-in-law in a few weeks for an off shore passage from San Francisco to
    San Diego and will use this as an opportunity to work on my noon sights
    while probably running mostly downhill, North to South. I've ordered
    Jim's book from Amazon.
    Thanks, 
    RC
    S/V Wayfinder
    
    -----Original Message-----
    From: NavList@fer3.com [mailto:NavList@fer3.com] On
    Behalf Of Hewitt Schlereth
    Sent: Wednesday, April 08, 2009 1:30 PM
    To: NavList@fer3.com
    Subject: [NavList 7885] Re: The Noon Fix
    
    
    Frank, here's  a second to your remarks re Jim's method. Jim, your
    book sounds very apt for today's realities - Celestial is bound to be
    in the 'if all else failz'  category. I'm off to Amazon to buy a copy.
    
    Hewitt
    
    On 4/8/09, frankreed{at}historicalatlas.com 
    wrote:
    >
    >  Jim, you wrote:
    >  " It is not a running fix, since no lines of position are advanced or
    retarded. Or even determined."
    >
    >
    > If you're adjusting the sights for motion of the observer, that is
    equivalent to a running fix. So unless you're explicitly reserving the
    expression "running fix" for the case of plotted LOPs, I don't think
    there's any problem calling it a running fix, and that may be helpful
    explaining the method to navigators who already understand that concept.
    >
    >  This whole business of generating a fix by a series of sights around
    noon is a subset of a general case which I have labeled (in the absence
    of previous terminology) a "rapid fire fix". If you take a series of
    multiple Sun sights, oner after another, over a fairly short time
    interval so that the Sun's azimuth changes by a moderate amount (let's
    say twenty degrees), then you can reduce these sights, perform a least
    squares analysis, and get a fix that is surprisingly accurate. This is a
    type of running fix since each sight has to be advanced/retarded based
    on the observer's motion.
    >
    >  In a general "rapid fire fix", the position is clearly more accurate
    in the direction of the Sun's azimuth just as the particular case of
    sights around noon yields a latitude that is more accurate than the
    corresponding longitude. The accuracy in the perpendicular direction is
    lower but increases rapidly either by multiplying the number of sights
    or by allowing for a larger change in azimuth.
    >
    >  -FER
    >
    >
    >
    >
    >
    >  >
    >
    
    
    
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