Abstract
A systematic series of measurements of the overall atmospheric modulation transfer function (MTF) combined with separate measurements of the turbulence MTF permits separation of turbulence and aerosol MTF components. While turbulence is generally dominant around midday, these results indicate that resolution through the open atmosphere is otherwise often limited by random small-angle light scattering by aerosols at least as much as or even more than by turbulence, depending on weather conditions and optical density.