a method that includes conditioning a radiation beam , imparting the radiation beam with a pattern to form a patterned radiation beam by a reticle having a pattern image area and a reticle mark , and projecting the patterned radiation beam onto a target portion of a substrate by a projection system . the method further includes illuminating the reticle mark by the radiation beam for generating an aerial image of the reticle , projecting the aerial image on an image sensor , collecting image data from the image sensor , obtaining from the image data positional parameters of the aerial image , and correcting any deviation of the positional parameters from a required position of the aerial image by compensating an illumination induced thermal expansion of the reticle by an estimated correction of magnification settings of the projection system , the estimated correction being calculated from a prediction of the temporal thermal expansion of the reticle .