Celestial Navigation · Sextant Corrections — Order
In what order are corrections applied to a sextant altitude (hs) to obtain observed altitude (Ho)?
- AApply dip first, then index error, then nothing else
- BApply the main altitude correction first, then dip, then index error
- CApply index correction and dip to get apparent altitude, then the main altitude correction (refraction/SD/parallax) to get Ho✓ Correct
- DApply all corrections simultaneously from a single table
Explanation
hs → apply index correction and dip → apparent altitude (ha) → apply the main altitude correction (refraction, plus semidiameter and parallax for sun/moon) → observed altitude (Ho). The almanac's main correction table is entered with apparent altitude.
Authority: Nautical Almanac; Bowditch (Pub. No. 9), the sextant altitude corrections
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