Measurement of the turbulence in the free atmosphere above Mt. Ma $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l}$$ danak

Abstract

Stellar scintillations were measured at Mt. Ma\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l}\)danak during 42 nights in 1998–1999 in order to estimate the contribution of the free atmosphere to the seeing. The atmosphere above 1–2 km provides a median seeing of \(0\mathop .\limits^{''} 39\), which is about one-third of the total seeing (\(0\mathop .\limits^{''} 70\)). The characteristic altitudes of turbulent layers are from 3 to 11 km above the summit, and the appearance of layers at altitudes of 3–4 km is accompanied by a degradation of the free-atmosphere seeing. The median isoplanatic angle is \(\theta _0 = 2\mathop .\limits^{''} 30\) (λ=500 nm, at the zenith). This is the first time that such data have been obtained for Ma\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l}\)danak.