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    Re: Sextants with Polarizing filters
    From: Frank Reed CT
    Date: 2006 Jan 30, 02:25 EST

    Joel Jacobs, you wrote:
    "There were limited  quantities of Navy MK II sextants made with polarizing
    filters for use in WW II.  Every once in a while one will surface."
    
    That's what got me wondering.  I've been playing with one of those recently,
    and it seems like an effective  design. Also, in the 1962 Bowditch, the first
    sextant pictured in article 1503  "Micrometer Drum Sextant" is a Navy Mk II
    with polarizing filters. The text in  this edition reads "Older sextants have
    two sets of shade glasses, as shown in  figure 1504. Many modern sextants are
    fitted with a single Polaroid filter of  variable darkness in place of each set
    of shade glasses, as shown in figure  1503a." Of course, it's not really a
    "single" Polaroid. It's a pair mounted in a  single unit --one with fixed
    orientation and the other rotatable.
    
    And you  wrote:
    " In general, they never really caught on in the navy or  out."
    
    Any speculation on why not? They seem convenient to me. If I had my  choice,
    I think I would prefer one standard shade of medium darkness and one
    polarizing unit for the greatest possible range of brightness reduction, in both
    locations where sets of shades are usually found on sextants.
    
    And you  wrote:
    "Capt. Sorreson of Coast and Simex fame was a proponent, and you see  many of
    the Simex brand, a private label, with them."
    
    I think I have a  cousin of a Simex sextant. It's marked "International
    Nautical", and it's a  Tamaya-alike in appearance. It's not a Simex by another
    name, is it? Despite its  rather "generic" branding, it has proven to be a
    remarkably accurate instrument  by every test I've subjected it to. It has nice,
    large polarizing units instead  of standard shades. The rotating parts were stuck
    rock solid after years in the  box (this instrument was apparently never
    used), and I half suspect that a  previous owner or two did not realize that the
    shades were polarizers at all.  There's a picture of one of these  here:
    http://www.nauticalantiquesandgifts.com/catalog/item/2418044/1886664.htm
    (mine  was a lot cheaper )
    
    Joel, you have apparently written on this  topic before on the list. I've
    found replies to your messages on 'Tamaya and  Simex' and all that in the list
    archives, but for some reason I can't find the  original message(s). So I would
    appreciate hearing what you know about  this.
    
    -FER
    42.0N 87.7W, or 41.4N  72.1W.
    www.HistoricalAtlas.com/lunars
    
    
    

       
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