Number of satellites visible in an exposure depending on the exposure time t_exp and the instrument field-of-view, specified by its circular radius R_fov = L/2. The effect of a discrete constellation of 10 000 satellites in a single orbital shell of 100 orbital planes and 100 satellites per plane at 1000 km altitude and 53° inclination is simulated for an observer at −30° latitude, observing towards zenith. The points are the results of the discrete simulations for different values of exposure time t_exp and field-of-view (). The solid lines are predictions based on Eq. (1).