On 10 April, your 1630 ZT DR position is LAT 21°03.0'N, LONG 63°11.0'W. You are on course 324°T at a speed of 22 knots. What will be the zone time of sunset at your vessel?
• Zone Time vs. Greenwich Mean Time (GMT/UT) and how longitude affects time • How to use the Nautical Almanac sunset tables for a given latitude, date, and longitude • How to compute run between times using speed and course to advance a DR position
• First, from the DR position and course/speed, decide whether you need to advance your DR to the time of sunset or assume sunset occurs close to your listed DR time. How would you check this in the Almanac? • Look up the time of sunset for 10 April at the nearest listed latitude and longitude. Is that time given in GMT (UT) or in Local Mean Time (LMT) for that longitude? • Once you have the base sunset time, how do you convert it to your ship’s zone time using the correct time zone description based on your longitude (east or west, and how many whole 15° zones)?
• Confirm you are using the correct time zone description (ZD) for longitude 63°11.0'W before converting times. • Verify you have applied any necessary interpolation in the Nautical Almanac for latitude and/or longitude if required by the table layout. • Before picking an answer, re‑check that the final time is in zone time (ZT) at the ship, not GMT/UT or LMT.
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