A number of refinements in ground-based optical telescopes and their detecting equipment, and also serious development of measures for neutralization of interference effects of the earth's atmosphere, permit the efficiency of observation of faint astronomical objects to be improved by at least an order of magnitude in the coming years. In the case of extragalactic astronomy and observational cosmology it is shown that progress in large ground-based optical telescopes has a decisive role in formation of contemporary concepts of the universe. Some of the problems of astronomy which will be solved by means of these instruments in the near future are discussed.