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    Bubble sextant at sea
    From: Noell Wilson
    Date: 2025 Jan 24, 05:26 -0800

    From John S. Letcher on, “everyone” says not to use a bubble sextant at sea. Letcher goes on to say that he wouldn’t expect better than +/- 20’.
    Maybe not bad if you’re truly lost mid ocean.

    See: https://www.usni.org/magazines/proceedings/1935/september/surface-navigation-bubble-octant

    Lieutenant Commander J. M. Sheehan, U. S. Navy in 1935 says that with much, much practice he could get good sights with a bubble octant.
    He doesn’t mention the type of instrument, ship, or the sea state. He mentions the ship rolling but refers to pitching as “minor”. I assume that the ship was fairly big.

    He mentions an inverted image and 5 minute graduations on the scale. I don’t recognize that instrument. He was a 1st Lieutenant at the time and a Lt. Commander in 1935 when he published. His temporary helper had time in square riggers. An old bubble sextant!

    In 1967(8?) DD931, our navigator had a long stretch with no horizon in the Atlantic. He later requisitioned a bubble sextant. (I had no interest in CelNav then and I’ve since imagined myself saving the day holding a pan of water as an AH or of taking a sight off the glassy sea. 😊) I don’t recall any later reports of good results with the bubble sextant.

    Regards, Noell

       
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