The devices and components of adaptive optical system ANGARA, which is developed for image correction in the Big
solar vacuum telescope (BSVT) at Baykal astrophysical observatory are described. It is shown that the use of
modernized adaptive system on BSVT not only reduces the turbulent atmospheric distortions of image, but also gives a
possibility to improve the telescope developing new methods of solar observations. A high precision Shack-Hartmann
wavefront (WF) sensor has been developed on the basis of a low-aperture off-axis diffraction lens array. The device is
capable of measuring WF slopes at array sub-apertures of size 640X640 μm with an error not exceeding 4.80 arc.sec.
Also the modification of this sensor for adaptive system of solar telescope using extended scenes as tracking objects,
such as sunspot, pores, solar granulation and limb, is presented. The software package developed for the proposed WF
sensors includes three algorithms of local WF slopes estimation (modified centroids, normalized cross-correlation and
fast Fourier-demodulation), as well as three methods of WF reconstruction (modal Zernike polynomials expansion,
deformable mirror response functions expansion and phase unwrapping), that can be selected during operation with
accordance to the application.