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    Re: Suitable Sextants
    From: Alexandre Eremenko
    Date: 2005 Oct 11, 13:01 -0500

    Joel,
    Thanks. It seems to me that in both cases it is the
    diameter of the telescope objective lens that is most relevant.
    Provided that the mirror occupies the whole field of view.
    Indeed, once this is the case,
    increased mirror will not send more light
    into the scope. Same about motion.
    
    So you probably mean that in the old sextants with small mirrors
    the mirrors did not occupy the full field of view,
    and some of this field of view was thus wasted, correct?
    
    Alex.
    
    
    On Tue, 11 Oct 2005 joel-jacobs@att.net wrote:
    
    > Hello Alex,
    >
    > Large mirrors collect more light and transmit more though the optics which 
    are an advantage in taking twilight sights.
    >
    > The second adavantage is that celestial objects tend to move around on the 
    horizon mirror due to the motion of the vessel or of the sight taker. They 
    also seem to move more when taking high altitude sights. The larger size 
    mirrors provide more surface area for the body to dance on before being lost 
    from view.
    >
    > Also try WD 40, a moisture displacement chemical, to minimize affects of spray.
    >
    > Joel
    > --
    > Visit our website
    > http://www.landandseacollection.com
    >
    >
    >
    >
    > -------------- Original message from Alexandre E Eremenko : --------------
    >
    >
    > > Dear Joel,
    > >
    > > > 1. The larger the size of the mirrors, the better.
    > >
    > > I always read and hear this, but I am not sure that
    > > I understand exactly why the larger mirrors are better.
    > > Can you explain?
    > >
    > > > 2. Sextants with enclosed tangent screws
    > > > are prone to having them freeze
    > > > unless they are cleaned after use when
    > > > there is spray.
    > >
    > > This I confirm, even with my small experience.
    > > The remedy is to wash it with fresh water after
    > > a spray. And the fresh water is sometimes scarce
    > > on a small boat.
    > >
    > > Alex.
    
    
    

       
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