Celestial Navigation · Sun Sight Procedure
When taking a Sun sight, 'swinging the arc' is done to ensure the:
- ASextant is vertical, so the lowest point of the body's swing touches the horizon✓ Correct
- BChronometer is wound
- CDeclination is correct
- DIndex error is zero
Explanation
Gently rocking the sextant makes the body swing like a pendulum; reading the altitude at the lowest point of the arc ensures the instrument is truly vertical, avoiding an over-reading from a tilted sextant.
Authority: Bowditch (Pub. No. 9), taking the sight
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