The method for determining the transmission of the lower layer of the atmosphere (6–7 km thick) is described, in which a light source with the spectrum d2W / dldλ ~ λ3 is formed by the Vavilov––Cherenkov radiation of charged particles of the extended atmospheric showers (EAS), in the process of the interaction between the cosmic rays and air atoms. Average transmittance of this layer in the wavelength range λ1 ÷λ2 = 300–800 nm obtained under favorable optical conditions of observation with the help of a Yakut integrated setup used for observing the extended atmospheric showers, are presented