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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant calibration (arc error)
From: Bill B
Date: 2005 May 14, 23:57 -0500
From: Bill B
Date: 2005 May 14, 23:57 -0500
Frank Agreed, if sextant parallax error is not a significant factor. My guess for 7/8/full-sized sextant-parallax-error average would be 0.1' at 1 nm. 3 arc seconds at 2 nm. Please let me know how you experiments turned out compared to star-to-star. Bill > I experimented with a method for testing arc error last week. Off > southeastern Connecticut there are numerous lighthouses seemingly at every > direction > around the horizon. So I measured all possible horizontal angles between five > of them and then compared. I'm still looking at the results, but for those of > you who want to look for arc error, this seems to be a good way to do it. It > follows from the simple fact that the angles should add up: if the angle from > lighthouse A to C is 120.1 degrees while the angle from A to B is 50.0 > degrees and the angle from B to C is 70.0 degrees, then there must be arc > error up > around the high end of the sextant arc. This sort of thing might serve as a > consistency check for tests done with star-star distances, etc.