🔍 Key Concepts
• Run a dead reckoning (DR) track from the 0800 fix to the time of the 0938 sight using course, speed, and elapsed time
• Convert chronometer time to GMT using the given chronometer error, then find GHA and Dec for the Sun at the time of the 0938 sight and work a standard sun sight for longitude
• Use the meridian passage (LAN) sight of the lower limb to determine latitude from meridian altitude, applying the correct dip, refraction, semi‑diameter, and declination corrections
💭 Think About
• First, compute the DR position at the time of the 0938 sight from the 0800 fix. How far (nm) do you travel in 1h 38m on course 285°T at 16.5 knots, and what is that DR position?
• From the chronometer reading and error, what is the correct UTC at 0938 zone time? Use that to derive a longitude line from the 0938 sight: is your longitude east or west of the assumed?
• For LAN at 1214 zone time, use the observed meridian altitude and Sun’s declination to compute latitude. Is the Sun north or south of your position on that date, and is it north or south of the equator in late March? That tells you whether to add or subtract declination.
✅ Before You Answer
• Confirm your time conversions: zone time → UTC using the correct time zone based on your approximate longitude, then apply chronometer error properly (fast vs. slow)
• Check that your course and distance run are correctly broken into latitude and departure components when updating DR positions
• Verify your latitude from LAN logic: correct use of LHA = 0°, correct sign of declination, and whether to use Ho of the lower limb plus semi‑diameter to get apparent center altitude before applying the meridian altitude formula