Exposure-Time Effects on Differential r0 Measurements

Abstract

Experimental results are presented indicating a causal effect between exposure time of the detection system and variations in measured differential stellar image motion. The variability is also dependent on atmospheric winds encountered along the entire propagation path at the precise time of measurement, making explicit comparison of experimental results with theory impractical. Earlier theoretical development is recast in terms of Fried's seeing parameter r0, and collected data is tested for conformance to stationarity criteria. It is recommended that atmospheric turbulence seeing monitors based on differential image motion measurements be restricted to exposure times of not more than two milliseconds.