Final answer:
Astronomers utilize the concept of a celestial sphere to divide the night sky, marking it with constellations that function like a grid. This helps to map the apparent east to west motions of the stars and other celestial bodies, as observed from Earth.
Step-by-step explanation:
Astronomers divide the night sky by imagining it as a large sphere surrounding the Earth, known as the celestial sphere. This sphere is a helpful tool for mapping out the positions of stars, planets, and other celestial objects. Distinct patterns of stars, known as constellations, are used to create a grid across this sphere much like longitudinal and latitudinal lines on a map of the Earth, aiding in the localization of astronomical objects.
The apparent motions of the stars are observed as if they rise in the east and set in the west due to the Earth's rotation. This motion makes it seem that the celestial sphere is turning around us. Understanding these concepts helps to identify constellations and comprehend the movement of the Sun, Moon, and planets across the sky from our Earth-based perspective.