Celestial Navigation · Hour Angle — Aries
The First Point of Aries (the reference for SHA) is best described as:
- AThe geographic position of Polaris
- BThe location of the sun at the summer solstice
- CThe point where the sun crosses the celestial equator going north at the vernal equinox — the origin for sidereal hour angle✓ Correct
- DThe point of the autumnal equinox
Explanation
The First Point of Aries is the vernal equinox — where the sun crosses the celestial equator moving north. SHA of a star is measured westward from Aries, and GHA Aries (tabulated hourly) plus SHA gives the star's GHA.
Authority: Bowditch (Pub. No. 9), sidereal hour angle and Aries
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