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    IE determination Freiberger Yacht Sextant.
    From: Herman Dekker
    Date: 2021 Sep 24, 07:36 -0700

    In prepartion for the Lunar Online Workshop on 6-7 nov for which
    I have registered. I wanted to know the Index Error of my Freiberger Yacht
    sextant. (Most sights I take from the backyard or in the Mountains
    in Germany, there I use the A-12 bubble sextant).

    I placed a cutted eyepiece of a solar glasses on the telescope with a rubberband.
    I got two equal colored suns in side, that confused me a little, which is the direct
    sighted sun, wich is the reflected sun?
    To solve this, I used the lightest horizon shade, so I know the darkest is the direct
    sighted sun. There is a little side error I guess 4’. What is max. permissible side error?

    Now I got one other problem, the reflected sun had a little shifted ghost image near it.

    Is this normal?

    I guess it is caused by the mirros, the mirrors have the reflecting coating not on the front
    but on the rear of the mirror. Is that the cause of the problem? Double refection?

    Will that problem disappear if I replace the mirror(s) with front reflective coating.
    I suppose for symmetry both mirrors must be front or rear reflective.
    Or is the sextant designed for rear reflective mirrors?

    Or is the little curved solarfilm (see photo) the cause of double sun.

    So a practical problem that more navigators must have solved?




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