Celestial Navigation · Hour Angle
For an observer in west longitude, Local Hour Angle is computed as:
- ALHA = GHA plus west longitude
- BLHA = GHA minus west longitude✓ Correct
- CLHA = west longitude minus GHA
- DLHA = GHA plus declination
Explanation
LHA = GHA − west longitude (or GHA + east longitude). If the result is negative, add 360°; if over 360°, subtract 360°. For sight reduction with Pub. 229 the assumed longitude is chosen so LHA is a whole degree.
Authority: Bowditch (Pub. No. 9)
Practice the full Celestial Navigation bank
Free spaced-repetition quizzing across 2190 USCG exam questions — it schedules your reviews so the ones you miss come back until they stick.
Related Celestial Navigation questions
- Hour Angle
An LHA of 000° means the body is:
- Hour Angle
Meridian angle (t) differs from Local Hour Angle (LHA) in that meridian angle is:
- Time
The Nautical Almanac tabulates the positions of celestial bodies against which time standard?
- Time
A vessel in west longitude has a zone description of +5. To convert zone time to UT you must:
- Coordinates
How is the GHA of a star obtained from the Nautical Almanac?
- Coordinates
Sidereal Hour Angle (SHA) is best defined as: