1. An apparatus, comprising: a projection lens having an object plane and an image plane; an optical wavefront manipulator configured to manipulate a wavefront in the projection lens; and a wavefront measuring device configured to measure a wavefront in the projection lens, wherein: the wavefront measuring device comprises a Moiré grating arrangement comprising an object grating and an image grating; the object grating is in the object plane; the image grating is in the image plane; the object and image gratings are configured to generate a Moiré superimposition pattern via an imaging of the object grating onto the image plane and the image grating; the Moiré grating arrangement is configured to simultaneously generate the Moiré superimposition pattern for a plurality of field points of an object field in the object plane and/or of an image field in the image plane; the optical wavefront manipulator is controllable on the basis of at least one measurement result of the wavefront measuring device; the wavefront manipulator is configured to correct a wavefront in the projection lens; the wavefront manipulator is configured to be controlled in a closed-loop; and the apparatus is a microlithography projection exposure.