Measurements of peak irradiances have been made in Los Angeles, California, nighttime atmospheres at distances from 0.90 to 6.77 statute miles from a Xenon flashlamp radiating uniformly in all directions. The measurements were made at wavelengths 0.40, 0.50, 0.77 and 0.88*m (microns) with receiver fields of view up to 64 degrees half-angle. From these data attenuation coefficients were calculated for collimated transmission and aureoled transmission (4*P source and flate receiver facing the source). Also calculated for aureoled transmission were values of R, the ratio of "scattered-in" radiation to direct radiation received by the flat receiver at various distances from the source. Angular scattering diagrams and attenuation coefficients for scattering were measured for radiation of wavelengths 0.40, 0.45, 0.50 and 0.55*m.