On 14 October your 0800 zone time (ZT) dead reckoning position is LAT 28°22.0'N, LONG 161°17.0'E. Your vessel is on course 116°T at a speed of 17.5 knots. What is the ZT of local apparent noon (LAN)?
• Local Apparent Noon (LAN) occurs when the Sun is on your meridian (LHA Sun = 0°). • Relationship between longitude and time: 15° of longitude = 1 hour of time; 1° = 4 minutes. • Need to use the DR longitude at LAN, not just the 0800 longitude, because the vessel is moving.
• From your 0800 ZT DR position, estimate how far (in time) it will be until the Sun crosses your meridian based on your east longitude. • How will your course and speed between 0800 and LAN change your longitude, and therefore slightly change the ZT of LAN? • How do you convert between UTC (GCT) and zone time (ZT) using the zone description based on your longitude?
• Use the DR longitude at LAN, found by advancing your 0800 DR position along course 116°T at 17.5 knots for the estimated time to LAN. • Make sure you use the correct zone description (ZD) for approximately 161°E (nearest standard time meridian). • Convert the Sun’s Greenwich Hour Angle (GHA) at meridian passage on 14 October to the corresponding GMT, then adjust by ZD to get ZT, and compare with the answer choices.
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