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    Re: Calibrating a sextant scale
    From: Frank Reed
    Date: 2007 Dec 02, 23:30 -0500

    Dan Allen,
    you wrote (regarding calibrating by measuring angles between lighthouses
    that add up to some known angle, 360 degrees for starters):
    "where did you do this?  Perhaps a few such locations could be given on the
    list so we could go try this out..."
    
    I do this near Eastern Point in Groton, Connecticut at the mouth of the
    Thames River. I have to trespass a little to get the spot I like, but
    there's also some opportunities for checking some angles at Stonington Point
     --where you and a group of us shot lunar distances back in September, 2004.
    
    By the way, for those familiar with the English river of the same name, the
    Thames in Connecticut is pronounced to rhyme with Names. I've often wondered
    whether the English River was pronounced that way neary 400 years ago when
    the Connecticut estuary was named. This Thames separates Groton and New
    London, Connecticut. New London was once a thriving whaling port, then a
    small general port, but it died in the late 20th century. The Groton side of
    the Thames is home to the US Sub Base (barely saved from closure a couple of
    years ago), the USS Nautilus museum (first nuclear-powered sub), as well as
    the "Electric Boat" division of General Dynamics which still builds new
    nuclear submarines. All of this is about five miles west of Mystic, Noank,
    and Mystic Seaport.
    
    You also wrote:
    "PS - I see a new appendix in a future edition of Bowditch: a list of
    locations where sextant errors can be measured!"
    
    Well, maybe in some other book for sextant enthusiasts.
    
    I've been thinking of other possibilities. Bays and sounds are the best bet.
    I wonder if there's a good spot in San Francisco Bay. I've also wondered
    about the possibility of observing from the top of a small hill in
    relatively flat country, but if the objects are out of the horizon by half a
    degree or more, the error is too large. I did come up with another
    possibility: how about a nice dry lake bed? There are plenty that are flat
    as a pancake for miles. Set up posts around the radius of a circle at
    roughly equal angles, and voila, a sextant calibration observatory! Do you
    know if one would need special permission to go out onto the flats west of
    Great Salt Lake and drive posts into the ground? Or any of the So Cal
    lakebeds?
    
     -FER
    
    
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