🔍 Key Concepts

• Sidereal Hour Angle (SHA) definition and how it is measured on the celestial sphere • The role of the First Point of Aries as a reference for measuring celestial angles • Relationship between SHA, Local Hour Angle (LHA) of a star, and GHA Aries

💭 Think About

• Think about from which reference line or point on the celestial sphere SHA is measured, and in which direction (eastward or westward). • Consider how navigators use SHA in sight reduction tables: do they normally add or subtract SHA to relate a star’s position to Aries? • Ask yourself whether SHA’s definition directly involves the Sun’s position at the vernal equinox, or whether that description fits a different concept.

✅ Before You Answer

• Verify how SHA is defined in your nautical astronomy or navigation textbook diagram of the celestial sphere. • Check whether SHA is always measured in one specific direction (east or west) and from which reference circle. • Confirm the formula that connects LHA of a star, GHA Aries, and SHA before deciding if any option can be “All of the above.”