Characterizing atmospheric turbulence with the lunar step response method

Most methods that astronomers use to characterize the strength of atmospheric turbulence in and around their observatories use differential image motion monitors observing a star to provide the necessary data for the measurement. With the Moon becoming a greater national priority, the need to characterize atmospheric paths between observatories on Earth and the Moon is potentially going to grow in the future. To this end, the differential image motion monitor is not an ideal instrument for characterizing turbulence along paths between observatories and the Moon as the bright Moon makes it difficult to detect and locate stars in its vicinity. This paper investigates a novel method for estimating Fried’s seeing parameter, by using the edge of the Moon as a step function. Results show an accurate estimation of the atmospheric seeing with a standard deviation of less than 4 mm between estimates of the atmospheric coherence diameter made at the same time. The results are supported by tests conducted on measured data over multiple nights. The technique is compared to another image-based method for estimating the seeing using blind deconvolution.