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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Video: 19th century Sun compass
From: David Pike
Date: 2025 Feb 18, 11:21 -0800
From: David Pike
Date: 2025 Feb 18, 11:21 -0800
From Paul Hirose: An 1889 article by James Keeler notes the endless confusion due to surveys based on the magnetic needle. It suggests that every city ought to have a pair of monuments set on a true meridian, and require by law that surveyors test their compasses annually.
Yes indeed Paul
Magnetic variation is a tiny bit diurnal. If we did a very rare air-swing (I only ever did one) with a Hughes peri-sextant fitted with a vernier azimuth ring, we took a Decca fix for each heading and sent the times, positions, and altitudes to the then Admiralty Compass Observatory for their best estimation of variation at that time and place. DaveP
