Occultation

This is when one celestial body, passes in front of, and obscures, another.
This refers to the same type of phenomena as an eclipse. [Distinguish from eclipse] From precise timings by different observers (almost exclusively amateur astronomers), a wide variety of information about celestial objects can be determined, including: planetary atmospheres, coordinates of distant radio sources, dimensions of objects with extended disks, radio and X-ray objects, and the heights of lunar mountains lying near the limb of the Moon.