Celestial Navigation · The Nautical Almanac — Increments
The hourly GHA of the sun is tabulated on the daily pages, but your sight was at 14h 23m 18s GMT. How do you account for the 23m 18s past the hour?
- AApply the equation of time for the minutes
- BMultiply the hourly GHA by the minutes
- CAdd the GHA increment for 23m 18s from the Increments and Corrections (yellow) pages✓ Correct
- DIgnore it — GHA changes only by the hour
Explanation
GHA changes continuously (~15° per hour). The whole-hour value comes from the daily page; the increment for the additional minutes and seconds is taken from the yellow Increments and Corrections pages and added to obtain GHA at the exact moment of the sight.
Authority: Nautical Almanac, Increments and Corrections pages; Bowditch (Pub. No. 9)
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