The astroclimate of Maidanak Observatory in Uzbekistan

The atmospheric turbulence and meteorology of the Maidanak Observatory in U zbekistan are reviewed. Night time seeing was measured during the period Au gust 1996 - November 1999 with the ESO Differential Image Motion Monitor. T he median zenith seeing (FWHM.) for the entire period of observations is 0. 69 " 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 ". The best monthly median seeing, 0.62 ", is observed in November, The winter max imum of clear time is usually observed in February (up to 50%) with a FWHM of 0.77 ". During an additional site testing campaign (9 nights) organized in July 1998, the median wavefront, outer scale L-0 of 25.9 m and a median isoplanatir angle theta(0) of 2.48 " were measured with the Generalized See ing 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 tu a remarkably large atmospheric time constant. No correlation between wavefront velocity and the willd velocity at ground level was found. The good seeing, large is oplanatic angle and, especially, slow wind, place Maidanak Observatory amon g the best international astronomical sites fur high angular resolution obs ervations by interferometry and adaptive optics.