We have performed a large statistical study of the peak emission altitude of green O(1D2–1S0) (557.7 nm) and blue 1 N (427.8 nm) aurora using observations from a network of all-sky cameras stationed across northern Finland and Sweden recorded during seven winter seasons from 2000 to 2007. Both emissions were found to typically peak at about 114 km. The distribution of blue peak altitudes is more ...