Measurement of the probability of getting a lucky short-exposure image through turbulence

The probability P of getting a lucky short-exposure image through the atmosphere has been measured. This measurement was made by photographing two point sources separated by a length Δ corresponding to the resolution limit of the imaging system with an aperture D. r0 was measured simultaneously. The distance between the imaging system and the point sources was 6000 m. Six observers independently determined whether the sources were resolved. By changing D, a plot of P versus D/r0 was obtained. It is shown that ln P ~ (D/r0)2, as predicted by Fried [ J. Opt. Soc. Am.68, 1651 ( 1978)].