Impact from bright stars on the S/N achievable by a target galaxy I_E = 24.5 AB mag (extended source) when placed over a full Euclid FoV (, with a scheme of the 6 × 6 CCD mosaic layout superimposed) in a typical part of the Euclid RoI. The colour scale is the S/N of a target source placed in the field at that position. The degradation in S/N when the target galaxy is placed closer and closer to a bright star is evident. Left panel: I_E = 4 AB mag star with effects on almost 50% of the FoV, but science impacted on less than 10% of the FoV. The solid yellow area is where the target galaxy is at S/N < 14 (see text). Right panel: common stars of AB magnitude I_E = 8, 9, and 10, which have a very limited impact overall with respect to the FoV size: less than 0.1% of the FoV lost on average across the RoI.