Abstract
When deciding what telescopic power is required to find objects of interest on the ground while flying over the earth at relatively high speeds, the positive value of an increased magnification must be balanced against the negative effects of a decreased observation time and an increased movement rate. The relative trade-off between these two factors—magnification and time—was compared in a series of three studies in which photographic imagery was used to simulate a telescopic view of the earth from a spacecraft orbiting at 175 nautical miles. Target acquisition decreased as image scale factor decreased and as image movement rate increased. When a change in scale factor was inversely proportional to a change in observation time, the positive effects of an increased image scale factor tended to exceed the negative effects of a decreased observation time and increased image movement rate within the limits of this study. The theoretical and practical implications of these and other results are discussed.
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