🔍 Key Concepts

• Vernal equinox as the celestial reference point • Difference between right ascension and sidereal hour angle • How sidereal time relates to the observer’s meridian

💭 Think About

• Ask yourself: Which term specifically measures along the celestial equator starting from the vernal equinox? • Which of these quantities is commonly written in hours, minutes, and seconds instead of degrees? • Which terms in the options are times at a location or at Greenwich, and which are angles to a star?

✅ Before You Answer

• Identify which option is defined as an angle measured along the celestial equator from the vernal equinox • Check which options are primarily time scales (local or Greenwich) rather than angular coordinates • Confirm which coordinate is commonly expressed in time units (0h to 24h) instead of 0° to 360°