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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.
>
>George.
>
>=======================
>
>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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