Diurnal Variation of Sodium Dayglow at Poona

228-232The detection of sodium dayglow is an extremely difficult instrumental problem as the emission has to be detected in the presence of an overwhelming background which is larger by a factor of 10,000 or more. A Zeeman photometer incorporating the principles of resonance scattering and magnetic scanning was developed for surmounting these difficulties of detection. A total of 68 days of observations was secured using this instrument during the year 1976.A suitable sample of these data is analyzed to indicate the capability of the instrument. Our statistical analysis indicates that the dayglow can be detected by this instrument even under the above-mentioned adverse conditions of signal-to-noise ratio. The diurnal variation of the intensity of sodium dayglow was thereby deduced, which shows a symmetrical pattern around the noon as obtained by earlier investigators. The possible lines of improvements and analysis are indicated and discussed in the light of recent criticism on the method of Zeeman photometry