Illustration of the comparative depth of the CFHT and Euclid Perseus cluster observations (the featured galaxy is PGC 12254). This image indicates that our ground-based optical data (r-band here) match the Euclid data well, both for compact sources and extended emission. The detection becomes challenging from the ground towards the NIR, where the Earth sky brightness increases rapidly (CFHT z-band observations versus Euclid H_E-band here). The FoV per panel is 4′ by 4′.