The Sextant in Practice: Sun-Run-Sun explained
21 June 2023 · 52 min · 23K views
What this video covers
A navigator performs a "Sun-Run-Sun" celestial navigation sequence to determine a vessel's position while sailing in the North Atlantic. The process begins with an estimated position (EP) derived from dead reckoning, accounting for course changes made overnight.0:23 The navigator checks the sextant's index error by aligning the horizon at zero degrees and zero minutes, then measures the sun's altitude from the coach roof, 2.5 meters above sea level.2:36 Using a sextant, the navigator records the sun's altitude, correcting for the height of eye and index error to find the observed altitude.9:57 The procedure involves calculating the Greenwich Hour Angle and declination using a nautical almanac, then applying the H-249 sight reduction tables to determine the intercept and position line.15:57 The navigator plots these lines on a chart to establish a fix.44:14 The sequence is repeated near local noon to refine the position.31:30
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