Except for the centers of bright clusters of galaxies and particularly bright supernova remnants, most observations of extended sources will be photon limited, i.e., there will be insufficient detected events to make use of the full EPIC angular resolution ( FWHM on-axis) beyond the excision of point sources. Even bright sources will be photon limited at high and low energies where the instruments' effective areas are reduced. Spatial binning of the data will therefore be needed to pursue any significant scientific studies. The pixel size of the images produced by XMM-ESAS is , which is a fine enough sampling to provide sufficient flexibility for creative binning (e.g., binning by high-resolution optical data) and the removal of contaminating point sources. For comparison, the physical size of the MOS pixels are , while the individual events are stored in pixels. The physical size of the pn pixels are , and are also stored in pixels.
If the ESAS package has been useful for the publication of your results, we would appreciate an acknowledgment in your paper. It will help with our statistics and the justification for the continued maintenance of ESAS, and the existence of the XMM GOF.