On 16 September your 0600 ZT fix gives you a position of LAT 29°47.2'N, LONG 65°28.4'W. Your vessel is on course 242°T and your speed is 13.5 knots. Local apparent noon (LAN) occurs at 1227 ZT, at which time a meridian altitude of the Sun's lower limb is observed. The observed altitude (Ho) for this sight is 63°25.3'. What is the calculated latitude at LAN?
• Meridian passage (LAN) latitude formula using Sun’s declination and Ho • How to get Sun’s declination on 16 September and whether it is north or south • Effect of run between 0600 and 1227 (DR latitude at LAN vs. latitude from sight)
• From the meridian altitude sight, how do you relate Ho, the Sun’s declination, and your latitude when the Sun is south of you? Think about the basic LAN latitude relationship. • Is your DR latitude at 1227 ZT exactly the same as at 0600 ZT? How far have you moved in latitude on course 242°T and 13.5 knots? • Once you find the latitude from the sight, compare it to your DR latitude at LAN. In this case, should the sight latitude be a bit more north or south than the DR? Why?
• Confirm the Sun’s declination for 16 September (and if it’s N or S). • Compute the DR latitude at 1227 ZT from the 0600 ZT fix, considering course and speed. • Apply the correct LAN latitude formula and sign convention depending on whether the Sun is to the south or north of your zenith.
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