N. N. Botygina

Shack-Hartmann sensor based on a low-aperture off-axis diffraction lens array

A Shack-Hartmann type wavefront sensor designed on the basis of a low-aperture off-axis diffraction lens array is described. Tests experiments showed that the sensor is capable of measuring wavefront slopes at array subapertures of size 640×640 µm with an error not exceeding 4.80 arcseconds (0.15 pixel), which corresponds to the standard deviation (SD) (SD = 0.0170λ) at the reconstructed wavefront. Advantages of the array used in the sensor and the technology of its manufacture are discussed. The sensor tested in the experiments can be used to measure atmospheric turbulence parameters and as an element of adaptive optical imaging systems.

Path-averaged differential meter of atmospheric turbulence parameters

A path-averaged differential meter of the structure constant of the atmospheric refractive index, Cn2, has been developed and tested. The results of a model numerical experiment on measuring Cn2 and the horizontal component of average wind velocity transverse to the path are reported.

Estimation of the astronomical seeing at the large solar vacuum telescope site from optical and meteorological measurements

Results of synchronous optical and meteorological measurements of Fried’s coherence length at the Large Solar Vacuum Telescope are presented. A decrease in this parameter in winter time is revealed. Spectra of wind speed and temperature inhomogeneities are studied during measurements of the Fried’s length.

Adaptive optical system for a ground-based solar telescope

This paper discusses a modified adaptive optical system for a ground-based solar telescope that corrects the influence of the atmosphere and of technical distortions on the quality of the resulting image of the object. An adaptive optical system is developed from traditional optoelectronic systems by incorporating additional elements, namely a wave-front corrector (an active mirror), a device for measuring wave-front distortion (a wave-front sensor), and a reference source that provides an optical signal to set the wave-front sensor. The angular resolution of an image in the telescope can reach diffraction resolution as a result of adaptive correction; i.e., it can be increased by about a factor of 10-25.

Simultaneous measurements of structure characteristics of atmospheric refraction by optical and acoustic methods

Comparative measurements of the turbulence level were carried out in the surface layer by optical and acoustic methods with the use of equipment designed at Zuev Institute of Atmospheric Optics. The turbulence level in the surface layer was studied at a height of 1.65 m. A stable difference between optical and acoustic data has been found.

Modified correlation tracker algorithm for tip-tilt correction system and project ANGARA on the Big Solar Vacuum Telescope

The possibility of applying adaptive correction to ground-based solar astronomy is considered. Several experimental systems for image stabilization are described along with the results of their tests. As a result of the installation of the first order adaptive-optics system, the Big Solar Vacuum Telescope (BSVT) acquired the new quality. Different ways of development of an adaptive correction to be used in the BSVT of the Baikal Astrophysical Observatory are discussed.

Adaptive optics system for solar telescope operating under strong atmospheric turbulence

New results obtained within Russian Science Foundation Project no. 15-19-20013 are presented. The project was started in the middle of 2015 and is aimed at the solution of actual problems of the development of the optoelectronic industry using adaptive optics for astronomy, laser, and other applications. The progress in the development of the up-to-date adaptive optics system for the largest Russian solar telescope, i.e., the 1-m Big Solar Vacuum Telescope of the Baikal Astrophysical Observatory, is described.

Passive optical methods in measurement of the structure parameter of the air refractive index

A passive optical method for estimating the level of atmospheric turbulence (structure parameter of the air refractive index Cn2) from the image jitter is considered. It is proposed to use a high-speed digital video camera and effective two-dimensional parallel algorithms of image processing for measuring Cn2 in real time. Results obtained by the active and passive optical methods, as well as by an acoustic method, are compared.

Seasonal variability of the astronomical seeing on the Large Solar Vacuum Telescope

The results of optical measurements of the quality of astronomical seeing on the Large solar vacuum telescope (LSVT) in spring and summer are shown. It is noticed that in the summer measurements, the quality of vision is higher on average 2.5 times than in the spring. Information on the seasonal variability of the astronomical quality of vision can be useful in the planning of scientific experiments for the LSVT, as well as to improve the performance of existing adaptive system

Joint measurements of atmospheric turbulence level with optical and acoustic meters

Complex measurements of atmospheric turbulence level were carried out with the use of a differential turbulence meter, a wavefront sensor, and ultrasonic weather stations. The refractive index structure constant was measured daily along horizontal optical paths at the Basic Experimental Station of the V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences. The comparative analysis of the data received is given.