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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: The Plane Scale and Stereographic Projection in Early Navigation
From: Brian Walton
Date: 2024 May 30, 01:59 -0700
From: Brian Walton
Date: 2024 May 30, 01:59 -0700
Robin,Lars,
A masterful paper on early techniques for construction using only Gunter scales, dividers, and drawing compasses.
You show how to derive values for great circle distances and bearings, via zenith distance. For sight reduction, ZD can of course be converted to Hc, and compared with Ho. This can be used to find ex-meridian corrections, time longitude, Sumner lines or St Hilaire intercepts, by simple plotting. All the navigation calculations solved by drawing, by 1647!
Recent attempts to produce better scales than Gunter on sliderules seem to have petered out. Sight reduction went the way of tabulated versines or haversines. Perhaps as I have suggested, navigation sliderules should have haversine scales, to minimise movements.
1647
