🔍 Key Concepts

• Amplitude of the Sun: relationship between observed compass bearing at the celestial horizon and the Sun’s true bearing (true amplitude) computed from latitude and declination • Use of the formula for true amplitude: ( \sin A = \frac{\sin \delta}{\cos \phi} ), where (A) is amplitude, (\delta) is Sun’s declination, and (\phi) is latitude • Conversion chain: compass bearing → magnetic heading → true bearing using variation and deviation, and how to solve that chain when some parts are known

💭 Think About

• From the DR latitude and the date (28 September), what is the Sun’s approximate declination, and how does that let you compute the true amplitude at sunset? • Once you have the Sun’s true bearing at the celestial horizon, how do you compare that with the observed compass bearing (273° psc) to find the total compass error? • When you know variation (6° W) and you have found total compass error, how do you separate that total error into variation + deviation, and determine the sign (E or W) of the deviation?

✅ Before You Answer

• Be sure you’re working with amplitude from due West, not from true North; amplitude is measured from the East/West point toward the Sun on the horizon. • Keep track of signs carefully: decide whether you are applying variation East/West and deviation East/West in the correct direction when converting between compass, magnetic, and true. • Confirm that you use the Sun’s center on the celestial horizon condition, which means you do NOT apply dip or refraction corrections to the observed bearing (those apply to altitudes, not bearings).