Celestial Navigation · Ex-Meridian — Concept
An ex-meridian sight is used when:
- AThe body is exactly on the meridian
- BThe body could not be observed exactly at meridian passage, so a sight slightly before or after is reduced to give latitude✓ Correct
- COnly stars are visible
- DThe sextant has no index error
Explanation
If clouds or other factors prevent a sight at the exact instant of meridian passage, an ex-meridian sight taken a short time before or after LAN is reduced (with a small correction for the body being off the meridian) to still yield a reliable latitude.
Authority: Bowditch (Pub. No. 9), Ex-Meridian Sights
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