DURING September, October 1971 and April 1972 we observed a narrow region of the night sky spectrum in the vicinity of the 5183.62 Å MgI wavelength. Measurements were made with a scanning Fabry-Perot interferometer1,2 from the observatory at Izaña on Tenerife, Canary Islands, and consisted of spectral scans of up to 4 Å wide centred on the MgI wavelength. In all, some 350 spectra were obtained. Because the primary aim of the experiment was to study the zodiacal light, all spectra were recorded between evening and morning twilights, and most in the ecliptic plane. None was recorded during twilight.