... Previous: Substepping and its Application to HST Imaging . ... This is a preliminary report on an application of the co-addition technique based upon the Richardson-Lucy algorithm. The combination of high signal-to-noise ground-based images obtained with the ESO NTT using SUSI with high angular resolution HST FOC f/96 images gives new insights on the properties of galaxy cores and their potential time variability. Cores of galaxies are one of the main thrusts of present extragalactic research. ...