On 17 January your 0730 zone time fix gives you a position of LAT 22°26.0'S, LONG 152°17.0'E. Your vessel is steaming on a course of 116°T at a speed of 17 knots. An observation of the Sun's lower limb is made at 1015 zone time. The chronometer reads 00h 13m 23s, and the chronometer error is 01m 49s slow. The observed altitude (Ho) is 66°02.1'. LAN occurs at 1152 zone time and a meridian altitude of the Sun's lower limb is made. The observed altitude (Ho) is 87°54.2'. Determine the vessel's 1200 zone time position.
• Run a DR track from the 0730 fix to 1015 and then to 1200 on course 116°T at 17 knots • Use the 1015 Sun sight (Ho = 66°02.1') with correct GMT to find a line of position and compare it to your DR longitude • Use the LAN meridian altitude (Ho = 87°54.2') at 1152 to find latitude from the Sun’s declination on 17 January
• From 0730 to 1200, how many hours run do you make at 17 knots, and what total distance along 116°T does this represent? • What is the correct GMT of the 1015 sight after applying chronometer error, and how does that help you get the Sun’s GHA and declination to check longitude? • For the LAN sight, how do you use Ho and the Sun’s declination to determine latitude in your hemisphere, and how does that compare to the 0730 latitude plus your DR track?
• Be sure you apply chronometer error with the correct sign to get accurate GMT for the 1015 sight • Confirm your time intervals: 0730–1015, 1015–1152, and 1152–1200, each converted correctly to decimal hours for distance run • Check that your final 1200 position is consistent: the latitude change must match the north‑south component of your DR track, and the longitude change must match the east‑west component plus any correction from the morning Sun sight
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