🔍 Key Concepts

• Sun azimuth problem – using DR position, GMT, and Nautical Almanac to find the Sun’s true bearing (Zn) • The correction chain T → V → M → D → C (True, Variation, Magnetic, Deviation, Compass) and the rules “west is best, east is least” • How to interpret a bearing given per standard compass (psc) and relate it back to magnetic and true bearings

💭 Think About

• First, think about how you will obtain the Sun’s true bearing (Zn) at the time and DR position: what information do you get from the chronometer (with error) and from the Nautical Almanac? • Once you have the true bearing of the Sun, how do you step through the sequence with variation and deviation to arrive at a compass bearing? Or, starting from the observed compass bearing, how do you work backwards to find deviation? • Pay close attention to the signs of variation and deviation: with a westerly variation, when going from True to Magnetic, do you add or subtract? How about when going from Magnetic to Compass with westerly or easterly deviation?

✅ Before You Answer

• Confirm the correct GMT (UTC) by applying the chronometer error (fast/slow) and make sure it matches a reasonable time difference from 1554 zone time for the longitude given. • Make sure you apply variation correctly: for 3° W variation, verify whether you add or subtract when going from True to Magnetic. • Before choosing an answer, write out the full correction line (e.g., T → V → M → D → C or the reverse) with numbers and check whether your final deviation sign (E or W) agrees with the algebra you used.