Celestial Navigation · Amplitudes
An amplitude observation of a body is taken when the body's center is:
- AAt the observer's zenith
- BOn the celestial horizon (theoretically rising or setting)✓ Correct
- CAt its maximum altitude on the meridian
- DExactly 45° in altitude
Explanation
Amplitude is the angular distance of a body north or south of the prime vertical (the true east-west line), observed when the body's center is on the celestial horizon. It is most often taken on the Sun at theoretical sunrise or sunset.
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
- 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:
- Coordinates
Declination of a celestial body is the celestial equivalent of:
- The Nautical Almanac
Approximately how fast does the GHA of the Sun increase with time?