How can astronomers locate objects in the sky?

by using distance and compass directions

by using latitude and longitude

by using altitude and zenith

by using the celestial sphere and constellations

Astronomers describe the position of objects in the sky by using coordinates ... The easiest way to do this is to use coordinate systems which assume that all objects in space are at the same distance, on the inside of an imaginary celestial sphere.

by using the celestial sphere and constellations

Explanation:

The astronomers use the coordinate systems to describe the position of the objects in the sky and the easiest way is to assume that the objects are at the same distance as with the reference to the celestial plane or the sphere and constellation.