On 25 December your 0330 ZT DR position is LAT 25°15.0'N, LONG 32°16.0'W. You are on course 145°T at a speed of 20 knots. What will be the zone time of sunrise at your vessel?
• Using your DR (dead reckoning) track to find your vessel’s position at sunrise time, not at 0330 ZT • How longitude affects time (4 minutes per degree of longitude from the standard meridian of your time zone) • Using the Nautical Almanac sunrise tables for the correct date and latitude
• From 0330 ZT onward, how long (in hours and minutes) will you steam on course 145°T at 20 knots before sunrise occurs? • How do you convert the Almanac’s sunrise time (usually given in GMT/UT for a specific longitude band) to local zone time at your actual longitude? • Is your ship east or west of the central meridian of your time zone, and should that make sunrise earlier or later in zone time?
• First compute the DR position at approximate sunrise time using Speed = Distance / Time, not just the 0330 position • Make sure you’re using the correct time zone description (ZD) for longitude 32°16.0'W (check which standard meridian that longitude falls closest to) • After applying longitude corrections to the Almanac sunrise time, re-check that your final time is reasonable for late December at about 25°N (roughly around 0600–0700 local)
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