Celestial Navigation · Altitude Corrections — Order Recap
The observed altitude (Ho) is obtained from the sextant altitude by applying corrections in the order:
- AAll at once in any sequence
- BRefraction first, then index error
- CParallax, then dip, then index error
- DIndex error and dip first (to get ha), then the main correction (refraction/SD/parallax)✓ Correct
Explanation
From hs: apply index error and dip to reach apparent altitude (ha); then take the main altitude correction (combining refraction, semidiameter, and parallax) using ha to reach Ho. The order matters because the main-correction tables are entered with ha.
Authority: Nautical Almanac; Bowditch (Pub. No. 9)
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