Celestial Navigation · Sextant Corrections
In reducing a sextant altitude (Hs) to observed altitude (Ho), the corrections are applied in which order?
- ARefraction, then dip, then index error
- BIndex error and dip first (to get apparent altitude), then the main altitude correction✓ Correct
- CSemi-diameter first, then dip, then index error
- DParallax first, then refraction, then dip
Explanation
Apply index error and dip to Hs to get apparent altitude (Ha). Then apply the main correction (which combines refraction, semi-diameter, and parallax from the Almanac altitude-correction tables) to Ha to get Ho.
Authority: Nautical Almanac
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