Paper detail

Study on atmospheric optical turbulence above Mt. Shatdzhatmaz in 2007--2013

We present the results of the atmospheric optical turbulence (OT) measurements performed atop Mt. Shatdzhatmaz at the installation site of new 2.5-m telescope of Sternberg Astronomical Institute. Nearly 300 000 vertical OT profiles from the ground up to an altitude of 23 km were obtained in the period November 2007 - June 2013 with the combined multi-aperture scintillation sensor (MASS) and differential image motion monitor (DIMM) instrument. The medians of the main OT characteristics computed over the whole dataset are as follows: the integral seeing $β_0 = 0.96$ arcsec, the free-atmosphere seeing $β_{free} = 0.43$ arcsec, and the isoplanatic angle $θ_0 = 2.07$ arcsec. The median atmospheric time constant is $τ_0 = 6.57 \mbox{ ms}$. The revealed long-term variability of these parameters on scales of months and years implies the need to take it into account in astroclimatic campaign planning. For example, the annual variation in the monthly $θ_0$ estimate amounts up to 30% while the time constant $τ_0$ changes by a factor of 2.5. Evaluation of the potential of Mt. Shatdzhatmaz in terms of high angular resolution observations indicates that in October--November, this site is as good as the best of studied summits in the world.