Аннотация:The calculation of astronomical-mirror distortions that occur during horizontal control is considered. The mirror is assumed to be suspended on a steel belt and to be loaded by the forces of its own weight and reactions due to the belt. The calculation is performed in terms of a flat shell of revolution of variable thickness, and the initial problem is formulated as the result of a superposition of the axisymmetric and skew-symmetric problems. The system of ordinary differential equations describing these problems is solved by computer. A displacement function is obtained which determines the shape of the optical surface of a belt-suspended mirror. Results are presented for calculations of three mirror variants.