🔍 Key Concepts

• Azimuth definition in celestial navigation • Relationship between azimuth and the observer’s horizon and meridian • Difference between a local meridian and the Greenwich meridian

💭 Think About

• When you measure an azimuth to a celestial body, what fixed direction do you start counting from on the horizon? • Which of the options represents a direction that is locally based on the observer, rather than a global reference used for time and longitude? • How is azimuth different from hour angle or zenith distance in terms of what it measures and where it starts?

✅ Before You Answer

• Confirm that azimuth is an angle along the horizon, not up toward the zenith • Identify which option represents the starting reference direction from which azimuth is usually measured (0°) • Eliminate any choices that describe a north–south line that is not tied to the observer’s location or that are vertical angles (like zenith-related) rather than horizontal directions