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    Re: Sextant scopes and an old-bold empiricist
    From: Gary LaPook
    Date: 2006 Apr 14, 13:51 -0700

    George Huxtable wrote:
    >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.
    >Yep, you're right about that one.
    Gary LaPook
    >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.
    >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.

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