EXPOSURE-TIME EFFECTS ON DIFFERENTIAL R(0) MEASUREMENTS

Experimental results are presented indicating a causal effect between exposure time of the detection system and variations in measured diffe rential stellar image motion. The variability is also dependent on atm ospheric winds encountered along the entire propagation path at the pr ecise time of measurement, making explicit comparison of experimental results with theory impractical. Earlier theoretical development is re cast in terms of Fried's seeing parameter, r(0), and collected data ar e tested for conformance to stationarity criteria. It is recommended t hat atmospheric turbulence seeing monitors based on differential image motion measurements be restricted to exposure times of not more than 2 ms.