🔍 Key Concepts

• Azimuth (Zn) in celestial navigation is the bearing of a celestial body from the observer, measured clockwise from a reference direction • For a sun sight, the azimuth angle is linked to the observer’s true horizon and a specific reference meridian or vertical circle • Distinguish between reference directions used in navigation (like true north) and geometric circles on the celestial sphere (meridians, vertical circles)

💭 Think About

• Ask yourself: In practical marine navigation, when we write an azimuth like Zn = 135°, what is that 0° reference that we measure clockwise from? • Which of the answer choices represents a standard universal reference used for bearings on Earth, rather than a local circle that depends on the observer’s position? • Think about how you would plot a sun azimuth on a chart: what line or direction on the chart does it start from?

✅ Before You Answer

• Verify which option corresponds to the standard reference direction for bearings in navigation (0° point for azimuths) • Confirm that azimuths in sight reduction tables and plotting sheets are measured from this same reference everywhere on Earth • Eliminate any options that describe local vertical circles through the zenith, rather than a global meridian used for bearings