Celestial Navigation · Amplitudes — Formula
The amplitude of a celestial body is found from sin(amplitude) = sin(declination) ÷ cos(latitude). For dec N20° at latitude 40°N, the amplitude is approximately:
- AE26.5°N✓ Correct
- BE20.0°N
- CE45.0°N
- DE13.0°N
Explanation
sin A = sin 20° ÷ cos 40° = 0.3420 ÷ 0.7660 = 0.4465, so A = 26.5°. The amplitude is named from east (rising) toward the pole of the declination's name: E26.5°N. True rising bearing = 090° − 26.5° = 063.5°.
Authority: Bowditch (Pub. No. 9), Amplitudes
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