The present invention is related to a method, a computer program, and apparatus for adapting an estimator for use in a microscope for estimating a position of an emitter in a sample based on a method, in which the sample is illuminated with light at one or more sets of probe positions and fluorescence photons are acquired for the sets of probe positions. The invention is further related to a microscope, which makes use of such a method or apparatus. The sample is illuminated with light at one or more sets of probe positions and fluorescence photons are acquired for the sets of probe positions. Photon counts of the acquired photons are then added to vectors of photon counts or sums of photon counts are determined for the sets of probe positions. A value representative of background noise is determined and used for adapting the estimator in real-time.