A Solar System body at opposition, on the opposite side of the Earth from the Sun.

A Solar System body, such as a planet, comet or asteroid, is at opposition when it is on the opposite side of the Earth from the Sun. The elongation of a Solar System body at opposition is 180 degrees.

The inferior planets, or other objects with orbits closer to the Sun than the Earth, can never be at opposition.

Searches for new faint Solar System objects, such as Kuiper Belt Objects and asteroids, often attempt to find these objects at opposition when they will have their maximum illumination by the Sun (i.e. their phase, if discernable, will be full).