All-spherical telescope with extremely wide field of view

An all-spherical catadioptic telescope with the angular field of view of several tens of degrees in diameter and spherical focal surface is proposed for the monitoring of large sky areas. We provide a few examples of such a system with the apertures up to 800 mm and the field of view $30^\circ$ and $40^\circ$ in diameter. The curvature of the focal surface is repaid by high performance of the telescope. In particular, the diameter of a circle, that includes 80% of energy in the polychromatic image of a star, is in the range $1.4'' - 1.9''$ across the field of $30^\circ$ size and $2.2'' - 2.9''$ for the field of $40^\circ$ size. Some ways of working with curved focal surfaces are discussed.