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    Re: Lunar Distances: Graphic Methods
    From: Henry Halboth
    Date: 2004 Apr 23, 12:24 -0400

    I have encountered somewhat vague references to instruments of sufficient
    accuracy on which the various entries necessary to the clearing of Lunar
    Distances could be entered and an acceptable result obtained. I have
    never actually seen such an instrument - pictured or otherwise.
    Many years ago, a system of plotting astronomical coordinates was
    proposed and actually developed under the head of "Spherographical (???)
    Navigation" and a book was published in connection therewith. This system
    used a plastic coated globe and finely calibrated, vernier equipped arcs
    for plotting; the idea being that Zenith Distances swung from carefully
    plotted Geographical Coordinates of observed celestial bodies would be
    used in position determination - accuracy obviously being proportionate
    to sphere size and instrument accuracy. I attended a lecture sponsored by
    the manufactureror of this system and can attest to the instrumentation
    being somewhat impressive at the time, and the demonstration certainly
    reasonably accurate. Obviously, the system never really caught on from a
    practical point of view but, in retrospect, it appears potentially
    useable for Lunar Calculations. I do recall a report by shipmates, that a
    spherical navigation system had been sighted aboard an old ship at some
    point in time but never got any details. Regardless, the theory is sound,
    whether practical or not.
    On Wed, 21 Apr 2004 22:59:13 -0400 Robert Eno  writes:
    > Henry Halboth wrote:
    > >
    > > I have also come across a graphical method of clearing the
    > distance, for
    > > which some degree of accuracy is claimed, and which is advocated
    > as a
    > > check against other calculations. This graphical solution was
    > being
    > > touted circa 1822 in Arnold's Lunarian - I really don't know or
    > remember
    > > if you have actual calculations made by L & C.
    > --------------
    > Robert responds:
    > Bruno Ortlepp wrote a very interesting paper on this subject
    > entitled
    > "Longitude Without Time" and which appeared in the Journal of the
    > Institute
    > of Navigation, Volume 16, No. 1, Spring 1969.
    > Eight years later, J.W. Luce submitted a paper on another graphic
    > lunar
    > method in Vol 24, No. 2, Summer 1977 of the same Journal.
    > Both are very interesting papers and worth the read. The allure of
    > these
    > methods lies in their simplicity and a circumvention of the drudgery
    > of
    > complex calculations. I have tried both methods but without much
    > success. I
    > have had much better results using the tables developed by Bruce
    > Stark.
    > You know you are in too deep when you start thinking about and
    > performing
    > lunars. Give up hope all ye who enter here.
    > Robert

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