In the horizon system of coordinates what is...

🔍 Key Concepts

• Horizon system of coordinates is based on the observer’s position, using altitude and azimuth • On the Earth, longitude measures position east or west along the equator/meridians • In the horizon system, one coordinate measures up–down from the horizon, the other measures around the horizon

💭 Think About

• First, decide: in the horizon system, which quantity tells you how far around the horizon a body is from a reference direction (like north)? • Which answer choices describe an up/down angle from the horizon, and which describe an around the circle angle? Match that ‘around’ angle to the role longitude plays on Earth. • Think about how you would fully describe the position of a star in the sky: which part of that description is most similar to saying a place is ‘30° west longitude’?

✅ Before You Answer

• Be clear that altitude is related to how high something is above the horizon, not around it. • Identify which option is an angle measured along the horizon from a reference direction. • Make sure you are matching “east–west position on a circle” on Earth with “position around the horizon circle” in the sky.

In the horizon system of coordinates what is equivalent to longitude on the Earth?

Altitude

Zenith distance

Azimuth angle

Horizon