Its altitude and ____ locate a star in the sky (7)
I believe the answer is:
azimuth
(Other definitions for azimuth that I've seen before include "Angular distance (in astronomy etc)" , "Horiz. angle (of compass bearing)" , "Arc of the sky from zenith to horizon" , "Direction of a compass bearing" , "Angle between vertical plane containing a celestial body and plane of the meridian" .)