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    Re: Sextant used on Graf Zeppelin
    From: Alan S
    Date: 2011 Mar 4, 10:27 -0800

    Tubular spirit-Ievel artificial horizons, whether straight or curved, have
    several serious limitations. Two tubes are required - one parallel to the
    plane of the instrument to establish the horizontal and one at right angles
    to deal with tilt of the plane of the instrument. ln the early designs, the
    observer had to look at three places at once: at the reflected image of each
    of the two bubbles and at the image of the celestial body reflecod in the
    horizon glass. A special lens was required to keep the eye focused on the
    bubbles at a few inches from the eye and at the same time, focused on the
    celestial body at infinio distance. Despite these disadvantages, Admiral
    Richard Byrd used a tubular spirit-Ievel artificial horizon mounted on a
    conventional sextant to establish his position in his flight over the North
    Pole in 1926. Brandis & Sons of Brooklyn produced a few of these
    instruments, but they were never widely successful.


    "Several serious limitations" might be an overly polite way of describing the operation, from the way it was described, looking at several things, at the same time, with one eye. That the thing worked at all, seemingly it did, strikes me as kind of amazing, alas man, for or with all his faults, turns out to be a fairly clever type, sometimes.

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