Celestial Navigation · Time — Watch Error
When a sight is timed with a comparing watch, the GMT of the sight is obtained by applying to the watch time the:
- ADip correction
- BEquation of time
- CWatch error on GMT (and chronometer error/rate if compared to the chronometer)✓ Correct
- DSemidiameter
Explanation
The comparing watch reading is converted to GMT by applying the watch error (found by comparison with the chronometer, itself corrected for chronometer error and rate). Accurate GMT is essential because 4 seconds equals 1' of longitude.
Authority: Bowditch (Pub. No. 9), timing the sight
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