Celestial Theory Part 12: The Stars
15. november 2021 · 17 min · 988 visninger
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Celestial navigation using stars relies on the First Point of Aries as a fixed reference point, which maintains a constant declination of zero degrees above the celestial equator.3:44 Because stars are distant, they lack parallax and semi-diameter, making them reliable for position fixing.1:35 Navigators use 58 selected navigable stars rather than identifying constellations.2:08 The modern method involves using Volume 1 of the Sight Reduction Tables, which provides pre-calculated height and azimuth for seven stars at a given latitude and local hour angle.13:06 By pre-setting a sextant to the predicted height and using a hand-bearing compass to orient toward the predicted azimuth, a navigator can locate a star without needing to identify it by name.15:37 The calculation process uses the Greenwich Hour Angle of Aries, adjusted by the star's Sidereal Hour Angle.8:20 While Air Sight Reduction Tables are commonly used for their convenience, they are limited to declinations under 30 degrees.9:32 The 2102-D star finder serves as a tool for those preferring the traditional identification method.11:31
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