🔍 Key Concepts

• Greenwich Hour Angle (GHA) of Aries and what it represents on the celestial sphere • Difference between GHA, LHA (Local Hour Angle), and SHA (Sidereal Hour Angle) • How local sidereal time relates to the position of the local meridian relative to Aries

💭 Think About

• Ask yourself: local sidereal time measures what angle between your local meridian and which reference point in the sky? • Which of the four choices directly expresses the angle between the local meridian and the First Point of Aries? • Think about whether sidereal time is tied to a global reference (Greenwich) or your local longitude, and how that affects the type of hour angle used.

✅ Before You Answer

• Verify which quantity uses your local meridian as the reference (not Greenwich). • Confirm which option describes an hour angle measured westward from your local meridian to Aries. • Eliminate any answers that use star-based offsets (SHA or right ascension) instead of directly giving an hour angle from your position to Aries.