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    Re: Noon sight for longitude
    From: Bill B
    Date: 2008 Jul 11, 04:28 -0400

    James N Wilson wrote:
    > George
    > Thanks for coming to my defense. You stated my objections precisely...
    Summing up the posts, there are any number of variables that must be
    accounted for to make the method of finding the moment of LAN by equal
    altitudes (or a symmetrical curve) viable.
    To those already stated, I might add other ghosts in the machine.  There are
    any number of posts from list members stating IE changes (hardly linear)
    during prolonged observations, even though the sextant was acclimated to the
    ambient temperature.  There is also an article on the CD that made the
    rounds years ago concerning Personal Corrections.  One set of research was
    conducted on a mountain top to minimize refraction changes, yet
    personal-correction factors changed over prolonged observations--even with
    rest periods.
    At least in the LAN video I mention in an earlier post, the female operating
    from a fixed position did mention re-calibrating the sextant (IE I assume)
    before the post LAN equal-altitude observation.
    Also valid, as suggested by Henry and George (in his 56d folding paper
    question), there are situations where a method is just not the right tool
    for the job.  In my N40 summer solstice example random scatter might produce
    acceptable results, where the same amount of scatter would not in George's
    N56 winter solstice scenario.
    Which raises, at least IMHO, the question of what constitutes acceptable
    results?  It is situational to be sure--near a rocky coastline vs. crossing
    an ocean. The only quantifiable standard to date was suggested by Frank,
    that being 1 nm latitude and 5 nm longitude.
    Lastly, as I continue to wrestle with a method whose current primary purpose
    is to provide a platform for intellectual gymnastics, I would appreciate any
    real-world input from the list members as to the range and standard
    deviation of scatter (under poor to great conditions) they experience.  An
    allied query, at what point when you are looking at your data do you cross
    the line between fix and EP?
    Bill B.
    Navigation List archive: www.fer3.com/arc
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