On 28 June your 1820 ZT DR position is LAT 16°00.0'N, LONG 31°00.0'W. You are on course 310°T at a speed of 18 knots. What will be the zone time of sunset at your vessel?
• Using the Nautical Almanac sunset tables for a given latitude and date • Converting between GMT (UT) and zone time (ZT) using zone description (ZD) based on longitude • Adjusting for longitude differences from the standard meridian used in the sunset tables (arc-to-time)
• Which table in the Nautical Almanac would you use to find the approximate time of sunset at LAT 16°N on 28 June, and what time scale is that table in? • What is the appropriate zone description (ZD) for LONG 31°W, and how do you use it to convert the sunset time from GMT/UT to ZT? • Is there any longitude correction needed between your actual longitude (31°W) and the standard meridian used for that zone, and how do you apply that correction in minutes of time?
• Be sure you are using the correct latitude band and date (28 June) in the sunset table. • Confirm the correct sign and value of the ZD for a position around 31°W before converting to ZT. • Check whether you must apply a longitude correction (difference from the standard meridian) and whether that correction should be added or subtracted from the tabulated sunset time.
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