Celestial Navigation · Hour Angle — LHA of a Star
To reduce a star sight, you need the star's LHA. Given GHA Aries, the star's SHA, and your longitude, how is LHA of the star found?
- ALHA star = GHA Aries + SHA − west longitude (or + east longitude)✓ Correct
- BLHA star = SHA − GHA Aries + longitude
- CLHA star = GHA Aries − SHA, ignoring longitude
- DLHA star = declination + SHA
Explanation
First form GHA star = GHA Aries + SHA, then apply longitude as for any body: subtract west longitude or add east longitude to get LHA. With an assumed longitude chosen to make LHA a whole degree, the result enters the sight reduction tables directly.
Authority: Nautical Almanac; Bowditch (Pub. No. 9), local hour angle of a star
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