Celestial Navigation: A Cockpit Conversation with RYA Yachtmaster Ocean Instructor Leon
October 27, 2024 · 22 min · 2K views
What this video covers
Leon Schulz, an RYA Yachtmaster Ocean instructor, explains celestial navigation in a cockpit conversation, covering the case for sextant skills, sextant mechanics, and the Sight Reduction Table method for calculating position without electricity.
He argues three reasons justify learning astro navigation: GPS vulnerability through jamming and spoofing (citing Baltic Sea disruptions and an Israeli student who fled the conflict zone specifically to learn sextant navigation), onboard power failure during storms when solar panels, wind generators, and diesel all fail simultaneously, and the seamanship tradition.2:15 A sextant, he explains, uses two mirrors — an index mirror and a horizon mirror — to measure the angle between a celestial body and the horizon; a full-view horizon mirror allows simultaneous see-through and reflection.4:50 Metal sextants from Bremerhaven cost €800–€2,500; plastic ones are unreliable.5:54 Three errors require periodic self-checking: Perpendicular Error, Side Error, and Index Error, with Index Error checked every session by setting the instrument to zero and aligning the horizon in both mirrors.8:20
For position calculation, Schulz advocates the Sight Reduction Table method — developed by the U.S. military in World War II for long-range bombers — over the trigonometric formula taught by Germany's SHS, which requires a calculator.10:26 The method compares a measured angle against the tabulated angle for a chosen Assumed Position; the difference in arc minutes equals nautical miles of distance.12:58 Two sights from different bodies, or two sun sights hours apart with a running fix applied, produce intersecting position circles.14:56 A six-day practical course runs in Malta each February.16:27
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