Astron. Astrophys. Suppl. Ser. 145, 293-304

The astroclimate of Maidanak Observatory in Uzbekistan

S.A. Ehgamberdiev^1,2 - A.K. Baijumanov¹ - S.P. Ilyasov¹ - M. Sarazin³ - Y.A. Tillayev¹ - A.A. Tokovinin^3,4 - A. Ziad⁵

Send offprint request: S.A. Ehgamberdiev

Correspondence to: shuhrat@astrin.uzsci.net

1 - Ulugh Beg Astronomical Institute of the Uzbek Academy of Sciences, Astronomicheskaya 33, 700052 Tashkent, Uzbekistan
2 - Max-Plank-Institute fur Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
3 - European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
4 - Sternberg Astronomical Institute, Universitetsky Prosp. 13, 119899 Moscow, Russia
5 - UMR 6525 Astrophysique, Université de Nice, Parc Valrose, 06108 Nice Cedex 2, France

Received April 28; accepted May 22, 2000

Abstract:

The atmospheric turbulence and meteorology of the Maidanak Observatory in Uzbekistan are reviewed. Night time seeing was measured during the period August 1996 - November 1999 with the ESO Differential Image Motion Monitor. The median zenith seeing (FWHM) for the entire period of observations is 0.69 $^{\prime\prime}$ at 0.5 $\mu$m. A maximum clear sky season for Maidanak is July - September, with about 90% of possible clear time and a median seeing of 0.69 $^{\prime\prime}$. The best monthly median seeing, 0.62 $^{\prime\prime}$, is observed in November. The winter maximum of clear time is usually observed in February (up to 50%) with a FWHM of 0.77 $^{\prime\prime}$. During an additional site testing campaign (9 nights) organized in July 1998, the median wavefront outer scale ${\cal L}_0$of 25.9 m and a median isoplanatic angle $\theta _0$ of 2.48 $^{\prime\prime}$  were measured with the Generalized Seeing Monitor developed at the University of Nice. The temporal evolution of the wavefront can be described by several layers moving at slow velocities with predominant direction from the West. This corresponds to a remarkably large atmospheric time constant. No correlation between wavefront velocity and the wind velocity at ground level was found. The good seeing, large isoplanatic angle and, especially, slow wind, place Maidanak Observatory among the best international astronomical sites for high angular resolution observations by interferometry and adaptive optics.

Key words: atmospheric effects -- site testing