A position on the Earth has a longitude of...

Question 1 of 2707066636ee928f7522a1c519e78

A position on the Earth has a longitude of 74°10'E. What would its celestial counterpart?

Question 1 of 27070

A position on the Earth has a longitude of 74°10'E. What would its celestial counterpart?

🔍 Key Concepts

• Difference between longitude and the celestial quantities GHA (Greenwich Hour Angle), LHA (Local Hour Angle), and SHA (Sidereal Hour Angle) • Which of these (GHA, LHA, SHA) are measured westward from a reference meridian and which from Aries • How a point with known terrestrial longitude is related to a celestial hour angle when projected onto the celestial sphere

💭 Think About

• Ask yourself: if you project a point on Earth straight up to the celestial sphere, which angle would describe how far west it is from the Greenwich meridian? • Which of the options involves a quantity that depends on local hour angle (needs an observer’s position) and which depend only on a fixed reference? • Which of these celestial angles (GHA, LHA, SHA) could directly equal a given longitude value without needing time or observer’s longitude?

✅ Before You Answer

• Make sure you know that SHA is measured westward from the First Point of Aries, not from Greenwich • Confirm whether LHA requires knowing the observer’s longitude as well as time, or if it is purely a property of a position • Verify which angles (GHA, LHA, SHA) can be numerically equal to a geographical longitude when describing the same meridian on the celestial sphere