  Whole atmosphere seeing \beta_0 is the most important parameter in site
testing measurements. Estimation of the seeing from a variance of differential
image motion is always biased by a non-zero DIMM exposure, which results in a
wind smoothing. In the paper, the wind effects are studied within short
exposure approximation, i.e. when the wind shifts turbulence during exposure by
distance lesser than device aperture. The method of correction for this effect
on the base of image motion correlation between adjacent frames is proposed. It
is shown that the correlation can be used for estimation of the mean wind speed
V_2 and atmospheric coherence time \tau_0. Total power of longitudinal and
transverse image motion is suggested for elimination of dependence on the wind
direction. Obtained theoretical results were tested on the data obtained on
Mount Shatdjatmaz in 2007--2010 with MASS/DIMM device and good agreement was
found.
