Celestial Navigation · Almanac — Declination Sign Change
When applying the d correction to a body's declination, the sign (add or subtract) is determined by:
- AWhether the tabulated declination is increasing or decreasing over that hour✓ Correct
- BThe observer's longitude
- CThe dip
- DThe equation of time
Explanation
The d value is the hourly rate of change of declination; its correction is added if the declination is increasing toward the next hour's value and subtracted if it is decreasing. The navigator checks the adjacent tabulated declinations to set the sign.
Authority: Nautical Almanac, Increments and Corrections
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