1.1.8 Photometry of the Zodiacal Light with the Balloon – Borne Telescope Thisbe

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We report on new measurements extending the spectral range of our earlier photometry (Frey et al. 1974) to the near ultraviolet. The residual extinction caused by atmospheric ozone was found to be 0.^m25 ± 0.^m13 (2950 Å) and 0^m36 ± 0^m13 (2150 Å) at 41.5 km float altitude. Within the errors of 10-30% arising from calibration and the reduction procedure our measurements at 5000, 3450, and 2950 Å are compatible to a colour of the zodiacal light not different from that of the sun. Our result obtained at 2150 Å is an upper limit, since no reduction of airglow and integrated starlight has been done yet at that wavelength. This upper limit is 30% above a solar-like spectrum. This result is not in contradiction to the 0A0-2 measurements (Lillie 1972). The strong intensity increase he found occurs at wavelengths below 2150 Å.