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    Wooden sextants. was; More on Lunars
    From: George Huxtable
    Date: 2008 Jul 9, 18:02 +0100

    Henry Halboth's thoughtful posting, [5753] in the thread "more on lunars" 
    raises lots of stuff to ponder, but I will ask here about just one aspect; 
    the question of wooden sextants. I've started a new threadname..
    He wrote-
     "I also certainly cannot believe that some of the earlier instruments made 
    of wood with ivory arcs, although works of art, could be relied on as 
    respects accuracy over a wide range of condition to be met at sea."
    Yes. They might have been well-calibrated when first made, but any wood, 
    even ebony, shifts over time as its wood, and its joints, age. It's the 
    long-term stability of a metal instrument that makes it worthwhile dividing 
    it to great accuracy in the first place.
    Henry continues- "Frank knows as well as I do that there were also wooden 
    sextants manufactured – how many I don’t know, but enough have wound up in 
    collections and museums to give us a good sample."
    That's the bit that specially interests me here. I don't doubt that such 
    wooden sextants were made; indeed, I've handled one. It was a particularly 
    small instrument, which you might think of as a "ladies' sextant", or 
    perhaps one intended for teaching small boys. Certainly, it didn't call for 
    wooden construction in order to minimise weight, if it was intended for use 
    by grown men!
    The excess angle-capability of a sextant, above the 90 degrees of the 
    quadrant / octant, was required only for measuring lunars, which called for 
    high precision, to at least some extent incompatible with a wooden 
    construction. So a wooden sextant was rather a contradiction. But how common 
    were they, ever? How many have "turned up in collections and museums", as 
    Henry claims?
    Here we have to be rather careful. Sometimes, a quadrant / octant can be 
    wrongly described or catalogued in a collection as a "sextant", even by an 
    experienced curator. Not because he's got it wrong, but because "sextant" 
    has become a generic, accepted name for all instruments of this family.
    And if they do turn up in a museum, does that indicate how common they were, 
    or (perhaps) how rare? Museums often like to show the unusual, rather than 
    the commonplace.
    Perhaps they were more common in American collections than in European ones. 
    After all, American mariners' technology had a lot of catching-up to do, a 
    history of having had to import precise instrumentation from Europe, and 
    well-developed woodworking skills. Silvio Bedini has written some useful 
    stuff about that, in "Thinkers and tinkers".
    So, I would like some enlightenment, please. Were wooden-framed sextants 
    indeed commonly used by American navigators, and are they commonly found in 
    American museums today?
    contact George Huxtable at george@huxtable.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    Navigation List archive: www.fer3.com/arc
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