Urban light pollution - The effect of atmospheric aerosols on astronomical observations at night

The transfer of diffuse city light from a localized source through a dust-laden atmosphere with optical depth less than 0.5 has been analyzed in the source-observer plane on the basis of an approximate treatment. The effect on several types of astronomical observation at night has been studied, considering different size distributions and amounts as well as particle shapes of the aerosols. The analysis is made in terms of the signal-to-noise ratios for a given amount of aerosol. The model is applied to conditions at the Wise Astronomical Observatory in the Negev desert, and limiting backgrounds for spectroscopy, photometry, and photography of stars and extended objects have been calculated for a variety of signal-to-noise ratios. Applications to observations with different equipment at various distances from an urban area of any size are possible. Due to the use of signal-to-noise ratios, the conclusions are different for the different experimental techniques used in astronomy.