
NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
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