The position of one of the superior planets when it is opposite the Sun in the sky, that is, when its elongation is 180í. At opposition planets are at full phase and reach their highest point in the sky at midnight. At the same time, they achieve their closest approaches to the Earth. As the orbits of the planets are elliptical rather than perfectly circular, some oppositions bring the planets closer to Earth than others. This effect is particularly marked with Mars.
