Observation of the day airglow

An unsuccessful attempt to observe the day airglow in the region 3000 to 9000 A with a small photographic spectrograph from n balloon has already been described by Wallace [1961]. A second instrument of higher resolution was flown on September 24, 1962; it was a Littrow spectrograph, using a 12-inch focal length f/2.5 aerial camera lens and a 600-groove/mm diffraction grating. The spectrum in the region 4500 to 7500 A was photographed in the second order with a reciprocal dispersion of 26 A/mm on an Eastman 103a-F plate; a gelatin filter was used to exclude the unwanted third order. A neon spectrum was photographed simultaneously with the sky spectrum, principally for the purpose of a performance test.