🔍 Key Concepts

• Greenwich Hour Angle (GHA) definition and how it relates to longitude • Relationship between west longitude and hour angles measured westward from Greenwich • How to convert an angle greater than 180° to an equivalent east/west longitude

💭 Think About

• Is GHA measured east or west from the Greenwich meridian, and how does that compare to how we label longitude (E/W)? • If a body's GHA is between 180° and 360°, what general hemisphere (E or W) will its longitude be in? • How do you find the difference between 360° and the given GHA, and what does that tell you about the numerical value of longitude?

✅ Before You Answer

• Confirm whether GHA is always measured westward from Greenwich on the celestial sphere • Check if a longitude close to 180° would make sense with a GHA of 210°30', or if it should be closer to 0° or 360° • Carefully subtract the given GHA from 360° and decide whether the resulting longitude should be labeled E or W based on GHA’s direction