The invention relates to an optical system, especially a projection light facility for microlithography, especially with an image field shaped as a slit or with non rotational symmetry illumination, comprising an optical element (1), especially a lens or a mirror, which is arranged in a mount (2) and actuators (3) which engage with the optical element (1) at least nearly perpendicular to the optical axis. The actuators (3) effect non rotational symmetric forces and/or moments deviating from the radial lines in the optical element (1) to generate deformations with substantially no changes in thickness. Image errors arising as a result of asymmetric heating of the optical system are compensated for by deformation of the optical element.