The angle taken counter-clockwise along the celestial equator from the First Point of Aries to the hour circle of the star is called what?

The angle taken counter-clockwise along the celestial equator from the First Point of Aries to the hour circle of the star is called what?

• A. Declination
• B. Polar Distance
• C. Right Ascension
• D. Zenith Distance

Answer: (C)

Right Ascension is the angular distance along the celestial equator from the First Point of Aries (the vernal equinox) to the star’s hour circle, measured toward the east. It functions like longitude on the celestial sphere and is usually expressed in hours, minutes, and seconds because the sky appears to rotate once every 24 hours. The hour circle of a star is the great circle through the celestial poles that passes through the star; where that circle meets the celestial equator defines the star’s Right Ascension. Declination measures how far north or south of the celestial equator a star is, Polar Distance is 90° minus declination (distance from a pole), and Zenith Distance is the angular distance from the observer’s zenith, so they describe different dimensions of position.

Right Ascension is the angular distance along the celestial equator from the First Point of Aries (the vernal equinox) to the star’s hour circle, measured toward the east. It functions like longitude on the celestial sphere and is usually expressed in hours, minutes, and seconds because the sky appears to rotate once every 24 hours. The hour circle of a star is the great circle through the celestial poles that passes through the star; where that circle meets the celestial equator defines the star’s Right Ascension. Declination measures how far north or south of the celestial equator a star is, Polar Distance is 90° minus declination (distance from a pole), and Zenith Distance is the angular distance from the observer’s zenith, so they describe different dimensions of position.