🔍 Key Concepts

• How to find meridian passage (LAN) time from your DR longitude and course/speed • Relationship between Greenwich hour angle (GHA) of the Sun and your longitude at LAN • How to convert between UTC, zone time, and longitude (time zone approximation: 15° per hour)

💭 Think About

• First, if the Sun is on your meridian at LAN, what must be true about the Sun’s GHA and your longitude at that instant? • From 0920 until LAN, your ship is steaming on 258°T at 18.5 knots. Is this heading taking you toward a greater or smaller east longitude, and how does that affect the LAN time? • Once you estimate the UTC of LAN from the Nautical Almanac idea, how do you adjust using your approximate time zone (based on your longitude) to get zone time?

✅ Before You Answer

• Compute how far (in degrees of longitude) your DR position will shift between 0920 and any candidate LAN time, using course and speed; be careful to adjust speed to longitude change using the cosine of latitude if needed • Check that at your chosen LAN time, your corrected longitude at LAN roughly matches the Sun’s GHA relation for meridian passage at that date • Verify that the final answer is in zone time, not UTC, and that the time zone used matches your central meridian (closest multiple of 15°) for 151°E longitude