Two Problems on the Principle of the Measurement of Seeing by Using the Differential Image Motion Method

A principled mistake in the principle of the differential image motion method described in the paper entitled "A new high speed two-dimensional CCD atmospheric turbulence monitor" by Waldie,A.H.et al.is pointed out,a correct practical equation is gi ven through the discussion and the principle is compared with our measured results.Then,we deal with another problem of this method: Need more than two apertures be used?