Lunar crater distribution from the Ranger 7 photographs

In a recent letter, Miller [1965] presented a size-frequency distribution obtained from one of the Ranger 7 photographs. He found that where N is the cumulative number of craters per 10 km2 having diameter greater than D meters. He explained that this represents a higher density than had been predicted earlier by McGillem and Miller [1962], who extrapolated over two or three orders of magnitude from earth-bound telescopic data, and he also suggested that the higher density was due to the formation of secondary craters on the moon. This letter is an attempt to extend his results.