This study of the optical effects of atmospheric turbulence concentrates on the stellar observation problem. When an infinite plane wave from an incoherent stellar source is sampled by an earth-based telescope, the resultant stellar image exhibits random fluctuations in intensity, position, and size due to turbulence-induced scattering in the intervening atmosphere. One familiar aspect of this problem is the scintillation of starlight apparent to the naked eye. The central aim is to express optical statistics in terms of refractive-index structure constant which pertains to strength of turbulence along the optical path. Data is presented on stellar and meteorological observations made between fall 1968 and spring 1969 with a 0.152-meter diameter refracting telescope. Data was recorded simultaneously on the three parameters of image intensity, motion, and size. The data is interpreted in terms of the theory and used to estimate strength of turbulence. The central result is a series of profiles for refractive-index structure constant along the vertical path. These are constructed using stellar data to calculate parameters of a model.