Journal Article

Differential image motion in the short-exposure regime

V. Kornilov and B. Safonov

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 418, issue 3, pages 1878-1888
Published in print December 2011 | ISSN: 0035-8711
Published online December 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19604.x
Differential image motion in the short-exposure regime

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The seeing β0 over the whole atmosphere is the most important characteristic for site-testing measurements. The estimation of the seeing using the variance of differential image motion is always biased by wind smoothing because of non-zero exposure of the differential image motion monitor (DIMM). This results in wind smoothing. In this paper, we study the wind effects within a short-exposure approximation (i.e. when the wind shifts the turbulence during exposure by a distance less than the device aperture). We propose a method for correcting this effect, based on the correlation of image motion between the adjacent frames. We show that the correlation can be used to estimate the mean wind speed and the atmospheric coherence time τ0. We suggest using the total power of the longitudinal and transverse image motion to eliminate the dependence on wind direction. The theoretical results obtained have been tested on data gathered at Mount Shatdzatmaz during 2007–2010 using the DIMM combined with multi-aperture scintillation sensor (MASS). Good agreement was found.

Keywords: atmospheric effects; site testing; techniques: miscellaneous

Journal Article.  7290 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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