O. N. Emaleev

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.

Image quality analyzer

Image quality analyzer (IQA) which used as device for efficiency analysis of adaptive optics application is described. In analyzer marketed possibility estimations quality of images on three different criterions of quality images: contrast, sharpnesses and the spectral criterion. At present given analyzer is introduced on Big Solar Vacuum Telescope in stale work that allows at observations to conduct the choice of the most contrasting images of Sun. Is it hereinafter planned use the analyzer in composition of the ANGARA adaptive correction system.

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.

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.

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.

Adaptive optics system application for solar 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. Using our work along several years and world experience in solar adaptive optics (AO) we are assuming to obtain first light to the end of 2008 for the first Russian low order ANGARA solar AO system on the Big Solar Vacuum Telescope (BSVT) with 37 subapertures Shack-Hartmann wavefront sensor based of our modified correlation tracker algorithm, DALSTAR video camera, 37 elements deformable bimorph mirror, home made fast tip-tip mirror with separate correlation tracker. Too strong daytime turbulence is on the BSVT site and we are planning to obtain a partial correction for part of Sun surface image.

Development of Components for Adaptive Optics Systems for Solar Telescopes

Wavefront aberrations at the entrance aperture of the Large Solar Vacuum Telescope were measured with a wavefront sensor of the adaptive optics system by a sunspot. To calculate the image shifts, a correlation algorithm with quadratic interpolation of the correlation function maximum position is used. The quality of astronomical vision, characterized by the Fried length, was estimated from the same experimental data as the statistical characteristics of the fluctuations of the coefficients of expansion of wavefront aberrations in Zernicke polynomials. The results were obtained at a Fried length of 51.6 mm in a sample 43 s long with a sampling frequency of 70 Hz. The means and standard deviations of the expansion coefficients are calculated. The analysis of the given spectra shows that the wavefront aberrations should be compensated in the frequency band 0–20 Hz for the effective correction of the images formed.