Celestial Navigation · The Nautical Almanac — d Correction
The 'd' value listed for the sun or a planet in the Nautical Almanac is used to correct the:
- AGHA, for index error
- BDeclination, for the minutes and seconds of GMT past the tabulated hour✓ Correct
- CLatitude, for refraction
- DHour angle, for dip
Explanation
The d value is the hourly rate of change of declination. Its correction (read from the Increments page against the minutes/seconds) is applied to the tabulated declination, with the sign determined by whether declination is increasing or decreasing.
Authority: Nautical Almanac, daily pages and Increments tables
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