Measurement of seeing and the atmospheric time constant by differential scintillations.
A simple differential analysis of stellar scintillations measured simultaneously with two apertures opens the possibility to estimate seeing. Moreover, some information on the vertical turbulence distribution can be obtained. A general expression for the differential scintillation index for apertures of arbitrary shape and for finite exposure time is derived, and its applications are studied. Correction for exposure time bias by use of the ratio of scintillation indices with and without time binning is studied. A bandpass-filtered scintillation in a small aperture (computed as the differential-exposure index) provides a reasonably good estimate of the atmospheric time constant for adaptive optics.
Tokovinin
Andrei
A
Cerro Tololo Inter-American Observatory, Casilla, La Serena, Chile. atokovinin@ctio.noao.edu