Question

Define the following terms:
(a) Zenith
(b) Nadir
(c) Celestial poles

Answer 1

(a) Zenith: The point on the celestial sphere that is vertically above the observer.
(b) Nadir: The point on the celestial sphere that is vertically opposite to the zenith.
(c) Celestial poles: The points where the axis of rotation of the Earth intersect the celestial sphere is called celestial poles.