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    Re: Sextant scopes and an old-bold empiricist
    From: George Huxtable
    Date: 2006 Apr 14, 15:10 +0100

    About finding the magnification of a sextant telescope, Gary LaPook wrote-
    
    
    | Or, if you can dissassemble the telescope, you can find the focal length
    | of the objective and of the eyepiece. Then the magnification is the
    | focal length of the objective devided by the focal length of the eyepiece.
    |
    | To find the focal length of these lenses simply focus the image of the
    | sun onto a piece of paper by adjusting the distance from the lense to
    | the paper until the edge of the image of the disk of the sun has sharp
    | edges as projected onto the paper. Measure the spacing between the lense
    | and the paper at this point and you then know the focal length of the lense.
    
    =====================
    
    
    All very well for two types of telescope; the inverting astronomical type and the prismatic.
    
    Not, however, for the Galilean, opera-glass scope, which you can tell because 
    it doesn't invert, yet is without the obvious bulges
    of a prismatic.
    
    For that type, the eyepiece is a diverger, not a converger. On its own, it 
    will not give an image of the Sun, or anything else, in
    the way that Gary describes.
    
    George.
    
    =======================
    
    contact George Huxtable at george---.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
    

       
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