Methods for characterizing atmospheric turbulence along an optical path from a laser transmitter to a laser receiver can include the steps of counting the number of laser speckles at the receiver imaging plane, and then finding Fried's parameter r0 using the counting result to characterize the turbulence along the path. Before counting speckles, images at the receiver image plane can be preprocessed by capturing the images. The captured images at the image plane can then be blurred and a threshold can be chosen so that only certain pixels in the image are further processed. The thresholding can be via Otsu's methods or via variants of a Gaussian fit. Kostelec's method can then be used to count speckles in the portions of the image that have made it through the thresholding step. Other counting methods could be used. Fried's can then be found using the speckle count.