On 20 November your 0612 zone time (ZT) position was LAT 25°38.0'N, LONG 166°54.0'W. Your vessel was steaming on course 126°T at a speed of 20.0 knots. An observation of the Sun's lower limb was made at 0854 ZT. The chronometer read 07h 51m 14s and was slow 02m 52s. The observed altitude (Ho) was 27°58.3'. LAN occurred at 1147 ZT. The observed altitude (Ho) was 45°35.0'. What was the longitude of your 1147 ZT running fix?
• Running fix using two sun lines with DR (dead reckoning) between observations • How longitude is determined from a meridian altitude (LAN) of the Sun • Effect of steaming course 126°T at 20.0 knots between 0854 ZT and 1147 ZT on your DR position
• From the first sun sight at 0854 ZT, where is your LOP (line of position) relative to your DR, and how do you advance that line to 1147 ZT? • For the LAN sight, how does the observed maximum altitude of the Sun relate to your latitude and, more importantly here, how do you get longitude from the time of LAN? • Once you have both (1) the advanced 0854 LOP and (2) the noon LOP, how do you plot them to get the running fix longitude?
• Carefully compute the run between 0854 ZT and 1147 ZT using ( \text{Distance} = \text{Speed} \times \text{Time} ) and apply it along course 126°T • Make sure you use the correct sign (E or W) when converting LAN time difference from zone time meridian to longitude • Check that the final running fix longitude is consistent with the DR track, i.e., it should not jump unrealistically east or west compared to the 0612 DR longitude
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