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    Re: Old Sextant on German money
    From: Nicolàs de Hilster
    Date: 2007 Mar 12, 08:44 +0100

    During one of my "basic survival at sea"-courses I worked with a square 
    signalling mirror that had a sort of handle with a string attached to 
    it. That handle had a small hole in it, just like the mirror on one of 
    the corners. The mirror also had a number of concentric circles around 
    that hole. The mirror and handle were connected with a piece of string 
    of about 25 centimetres that ran through those two holes. The whole idea 
    was to look through the hole in the mirror and through the hole in the 
    handle (the handle being further away from your face than the mirror) to 
    the object that needed your attention, then cast a projection of the 
    concentric circles on the hole in the handle. The string would help to 
    stabilize the whole set-up. This would then result in the reflected 
    light to be cast in the proper direction. It works about the same as 
    shining the light through the fingers of your other hand while pointing 
    in the proper direction as can be seen in attached images (The amount of 
    fingers to be used might vary on the country where you're in ;-)).
    
    Nicolàs
    
    
    
    Bill Noyce wrote:
    >> Every French yacht is
    >> required to carry a signalling mirror. It is just a plain round mirror about
    >> 12 - 15 cm in diameter with a hole in the middle. You turn in the direction
    >> of the sun and look through the hole. You then see a red point which marks
    >> the spot where you are just reflecting the sun rays.
    >>     
    >
    > The sun shines through the hole and makes a small spot somewhere on
    > your face, usually, and the back of the mirror is also silvered.  If
    > you move the mirror so the spot on your face is imaged at the hole,
    > then the front of the mirror is shining at whatever you see through
    > the hole.  I assume that's the mechanism behind the "red point"
    > Wolfgang mentions.  You need to be able to tell where your target is,
    > but you don't have to see the light shining on it.
    >     -- Bill
    >
    > >
    >
    >
    >   
    
    
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