Measuring Seeing from Solar Scintillometry and the Spectral Ratio Technique

In principle, the optical transfer function can be described by a single parameter, the Fried parameter r₀, which reveals the net effect of the turbulence along the line of sight. We present measurements of the Fried parameter obtained from the spectral ratio technique and compare them to data from solar scintillometry and from angle-of-arrival fluctuations. The measurements were performed at the Big Bear Solar Observatory (BBSO) in 1997 and 1998 – before and after a series of steps were taken to reduce dome seeing. The results show that the dome seeing was considerably reduced and now approaches the seeing conditions measured outside the dome. The Fried parameter as measured by the spectral ratio technique now frequently exceeds r₀=10 cm at our lake site observatory. Accounting for the remaining dome and window seeing, the scintillometer and the angle-of-arrival data imply the potential for an r₀>20 cm for BBSO during days of good seeing.