Celestial Navigation · Sextant Corrections — Parallax
Horizontal parallax is a significant altitude correction primarily for the:
- AStars
- BDistant planets only
- CMoon✓ Correct
- DPolaris
Explanation
Parallax in altitude corrects for the difference between observation from the Earth's surface and the center. It is large for the nearby Moon (horizontal parallax tabulated as HP), small for the Sun/planets, and negligible for stars.
Authority: The Nautical Almanac, Moon altitude correction tables
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