On 17 May your 0300 ZT DR position is LAT 27°21.0'N, LONG 146°14.0'E. You are on course 107°T at a speed of 18 knots. What will be the zone time of sunrise at your vessel?
• Zone Time (ZT) vs Greenwich Mean Time (GMT/UT) and how longitude determines your time zone • How to use the Nautical Almanac sunrise tables for a given latitude and date • How to apply longitude correction to convert from GMT of sunrise to Zone Time at the vessel
• From the vessel’s longitude, what is the appropriate time zone description (difference between ZT and GMT)? Is it a whole hour or do you need to consider anything special? • Once you get the GMT of sunrise from the almanac for 27°N on 17 May, are you correctly adjusting it for your exact longitude (east or west of the reference meridian)? • After converting GMT sunrise to ZT at the ship, does the result make sense compared to 0300 ZT DR position and expected daylight for that latitude in May?
• Confirm the correct time zone for 146°14.0'E using the standard 15° per hour rule and rounding to the nearest central meridian • Use the right latitude column and date in the sunrise tables, and interpolate properly if needed • Make sure to apply the sign of the time zone correctly when converting between GMT and Zone Time (east longitudes generally have time zones ahead of GMT)
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