Variation of [OI] emission (5577) on the night of 5/6 January 1951

Photoelectric observations of the nightglow on 5/6 January 1951 are analyzed and compared with similar observations made on the following night. The height of the oxygen layer, as deduced from the variation of Iz/Io with zenith distance, is 200±25 km. Comparison of observations in the east and west with an isophote map based on the remainder of the sky provides semi-quantitative support for the Roach-Pettit hypothesis that there is an apparent westward diurnal motion of a stable excitation pattern. A height of 300 km is indicated by the time required for a given emission area to progress from east to west.