Effective magnitude, M_eff, of a satellite with M_{1000 km} = 7 as a function of its altitude, for various exposure times (colors) and spectrograph aperture width (line style). Here, M_eff does not vary much with the elevation of the satellite above the horizon. Typical altitudes of the Star-link and OneWeb satellites are indicated. The detection limit of a series of ESO spectrographs (for a 1200s exposure) is indicated; an instrument will only be sensitive to satellites brighter than that level.