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    Re: Cannot focus sextant telescopes
    From: Bill Morris
    Date: 2016 Aug 2, 19:41 -0700

    David, you have now established that C is the eye tube belonging to the Keplerian (long tube), since a Galilean cannot use a graticule, as the eye lens is negative (concave). If you look belond the graticule, you should see another lens called the field lens. If F is a negative lens on its own it will give a small and erect  image in all circumstances. If it is a positive lens it will give a magnified image when used as a magnifying glass, but held at arms length it will give a small inverted image. If it is positive, it may belong with C and the eye lens at present with C may belong to A, though with an absent tube.

    Bill

       
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