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Kornilov V.,Universitetsky Prosp 13
Monthly Notices of the Royal Astronomical Society | Year: 2011

The atmospheric scintillation of stars is the main reason why the ground-based photometry of astronomical objects has limited accuracy. This becomes particularly noticeable for a variability study with amplitudes of the order of thousandths of stellar magnitude or less. We examine the problem of colour scintillation (i.e. fluctuations of the difference between light intensities measured simultaneously in two different photometric bands). We derive the relations between the colour scintillation power (index) and the atmospheric turbulence, telescope diameter and the characteristics of the photometric channels. Asymptotic dependences for large telescopes (1-10 m) are obtained, which allow us to predict the value of the colour scintillation for a particular telescope and detector. It is shown that the colour scintillation index is ∝D -3 for measurements with both short (milliseconds) and long (seconds) exposures. We estimate the impact of the atmospheric dispersion, which amplifies colour scintillation away from the zenith. We show that colour scintillation in the long-exposure regime depends strongly on the wind direction in the upper atmosphere. © 2011 The Author. Monthly Notices of the Royal Astronomical Society © 2011 RAS. Source

Kornilov V.G.,Universitetsky Prosp 13 | Kornilov M.V.,Universitetsky Prosp 13
Experimental Astronomy | Year: 2011

The altitude distribution of optical turbulence is derived from the MASS instrument data by solving an inverse problem. In this paper, some modifications of the profile restoration are described. The principal change is the introduction of the Non Negative Least Squares algorithm which has good regularizing properties. An averaging of scintillation indices was replaced with averaging of obtained solutions what leads to clearer physical results. It is shown that restoration with a number of turbulent layers as large as 14-15 can be successfully performed. © 2011 Springer Science+Business Media B.V. Source

Kornilov V.,Universitetsky Prosp 13 | Safonov B.,Universitetsky Prosp 13
Monthly Notices of the Royal Astronomical Society | Year: 2011

The seeing β0 over the whole atmosphere is the most important characteristic for site-testing measurements. The estimation of the seeing using the variance of differential image motion is always biased by wind smoothing because of non-zero exposure of the differential image motion monitor (DIMM). This results in wind smoothing. In this paper, we study the wind effects within a short-exposure approximation (i.e. when the wind shifts the turbulence during exposure by a distance less than the device aperture). We propose a method for correcting this effect, based on the correlation of image motion between the adjacent frames. We show that the correlation can be used to estimate the mean wind speed and the atmospheric coherence time τ0. We suggest using the total power of the longitudinal and transverse image motion to eliminate the dependence on wind direction. The theoretical results obtained have been tested on data gathered at Mount Shatdzatmaz during 2007-2010 using the DIMM combined with multi-aperture scintillation sensor (MASS). Good agreement was found. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS. Source

Kornilov V.,Universitetsky Prosp 13 | Shatsky N.,Universitetsky Prosp 13 | Voziakova O.,Universitetsky Prosp 13 | Safonov B.,Universitetsky Prosp 13 | And 2 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2010

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. © 2010 The Authors. Journal compilation © 2010 RAS. Source

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