Opposition
When a planet is opposite the Sun in our sky — at its closest and brightest, and up all night.
Mars, Jupiter, Saturn, Uranus and Neptune come to opposition when the Earth passes between them and the Sun. The planet rises at sunset, is highest around midnight and shows its biggest disk. Mars's oppositions come every 26 months, and some bring it much closer than others.
At the eyepiece
The weeks around opposition are the best time to observe a planet — but it's worth looking for months either side.