Paper detail

First results of site testing program at Mt. Shatdzhatmaz in 2007 - 2009

We present the first results of the site testing performed at Mt.~Shatdzhatmaz at 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 hours per year. Principle attention is given to the measurement of the optical turbulence altitude distribution which is the most important characteristic affecting optical telescopes performance. For the period from November 2007 to October 2009 more than 85\,000 turbulence profiles were collected using the combined MASS/DIMM instrument. The statistical properties of turbulent atmosphere above the summit are derived and the median values for seeing $β_0 = 0.93$~arcsec and free-atmosphere seeing $β_{free} = 0.51$~arcsec are determined. Together with the estimations of isoplanatic angle $θ_0 = 2.07$~arcsec and time constant $τ_0 = 2.58 \mbox{ ms}$, these are the first representative results obtained for Russian sites which are necessary for development of modern astronomical observation techniques like adaptive optics.