Learning Celestial Navigation - The Noon Sight for Latitude - How to master Astro Nav!
26 febbraio 2024 · 11 min · 2K visualizzazioni · Dominica
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A noon sight tutorial taken off the coast of Dominica on the March 20 vernal equinox demonstrates how to calculate latitude from a single sextant measurement of the sun at local apparent noon.1:42 The equinox setting lets the instructor show the simplest case first: zenith distance equals latitude when the sun is directly over the equator, yielding a measured altitude of 74°15′ and a computed latitude of 15°45′N, confirmed against GPS.3:18 A second special case, Lahaina Noon, is explained: when the sun reads 90° on the sextant, the observer's latitude equals the sun's declination drawn directly from the Nautical Almanac.4:44 The tutorial then defines declination as the latitude of any celestial body's geographic position and works through three general cases — sun in the opposite hemisphere, same hemisphere but closer to the equator, and same hemisphere but farther from the equator — with the formulas latitude = zenith distance minus declination, zenith distance plus declination, and declination minus zenith distance respectively.5:52 Three worked example problems use the 1981 Nautical Almanac, covering positions near the Yucatan Peninsula, Nova Scotia, and the Caribbean Sea, including declination interpolation between whole hours.7:11 Target accuracy for ocean crossing is stated as 15–20 nautical miles.10:23
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