Celestial Navigation · The Nautical Almanac
The 'd' correction in the Nautical Almanac is applied to the declination, and its sign:
- AIs always added
- BIs always subtracted
- CDepends on the time of day
- DDepends on whether declination is increasing or decreasing✓ Correct
Explanation
The d value gives the hourly rate of change of declination; the d correction is added if declination is increasing toward the next hourly value and subtracted if it is decreasing. The navigator determines the sign by inspecting consecutive hourly declinations.
Authority: Nautical Almanac
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