Synthetic SED from the PHOENIX library (Husser et al. 2013) of a star similar to WASP-189. The stellar properties are an effective temperature T_eff = 8000 K, a surface gravity logg = 4.0, and a solar metallicity. The stellar SED in blue is represented over the CHEOPS passband (330–1100 nm) shown as a black dotted line. The effective SED as seen by the CHEOPS instrument is the solid orange line, for which one can see that most of the energy lies within the 400–800 nm range and the contribution beyond 1000 nm is marginal.