First results of a site-testing programme at Mount Shatdzhatmaz during 2007–2009

We present the first results of site testing performed at Mt Shatdzhatmaz in the Northern Caucasus, where the new Sternberg Astronomical Institute 2.5-m telescope will be installed. An automatic site-monitor instrumentation and functionality are described, together with the methods of measurement of the basic astroclimate and weather parameters. The clear night-sky time derived on the basis of 2006–2009 data amounts to 1340 h per year. Principal attention is given to measurement of the optical-turbulence altitude distribution, which is the most important characteristic affecting the performance of optical telescopes. For the period from 2007 November–2009 October, more than 85 000 turbulence profiles were collected using the combined Multi Aperture Scintillation Sensor and Differential Image Motion Monitor (MASS/DIMM) instrument. The statistical properties of the turbulent atmosphere above the summit are derived and the median values for seeing β0= 0.93 arcsec and free-atmosphere seeing βfree= 0.51 arcsec are determined. Together with the estimations of isoplanatic angle θ0= 2.07 arcsec and time constant τ0= 2.58 ms, these are the first representative results obtained for Russian sites, and are necessary for the development of modern astronomical observation techniques like adaptive optics.