Optical Image Quality in a Turbulent Atmosphere

Abstract

Measurements of the time-average modulation transfer function of an optical system comprising an objective and a horizontal air path correlate with a parameter which characterizes the magnitude of temperature fluctuations in the lower layers of the atmosphere. Evidence is produced to support an exponential relationship between the transfer function and the atmospheric temperature structure function. The transfer function fluctuates rapidly about a mean; visual estimates of resolution limit agree more closely with the maxima than with the mean. The significance of these results is discussed in relation to the choice of conditions for good terrestrial and astronomical seeing.