At 1730 zone time, on 3 March, your DR position is LAT 16°00'S, LONG 80°00'W. You are steering 000°T at a speed of 7.5 knots. What is the zone time of sunset?
• Zone description (ZD) and how to determine it from longitude 80°00'W • How to find sunset LMT (Local Mean Time) from Nautical Almanac for a given date and latitude • How to apply the watch-to-ship (W→S) time diagram: DR longitude at event time vs. meridian longitude of tabulated data
• From 1730 ZT, estimate about when sunset will occur at 16°S in early March, then think how far that is from 1730. • Work out the DR longitude at the approximate time of sunset using course and speed; compare this with the longitude used to get the Almanac sunset time. • Convert the Local Mean Time of sunset to zone time using the correct zone description for 80°W and your DR longitude.
• Be sure you are using the correct zone description sign for west longitude when converting between ZT and GMT (UT). • Confirm you have corrected the DR longitude from 1730 to the approximate sunset time before entering the Almanac or doing the final time conversion. • Check whether the sunset time from the Almanac is in LMT at the ship’s meridian and not ST (standard time) or GMT.
No comments yet
Be the first to share your thoughts!