Celestial Navigation · Coordinates — GHA and Longitude
The geographic position (GP) of a celestial body is the point on Earth where the body is directly overhead. Its longitude corresponds to:
- AThe body's declination
- BThe body's SHA
- CThe body's GHA (converted to longitude — west of Greenwich when GHA is 0°–180°)✓ Correct
- DThe local hour angle
Explanation
The GP latitude equals the body's declination; the GP longitude equals its Greenwich hour angle expressed as longitude (GHA 0°–180° is west longitude; over 180° converts to east). The sight's circle of equal altitude is centered on this GP.
Authority: Bowditch (Pub. No. 9), geographic position of a body
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