LBT V optical data during secondary eclipse of WASP-33 b as a function of the orbital phase and the hours relative to mid-eclipse. Top: normalized flux. The continuous black line shows the best-fitting model (24+3 parameters). The error bars were enlarged to meet the scatter of the data. Bottom: residual light curve. Vertical dashed lines indicate first to fourth contacts assuming a circular orbit (Deming et al. 2012).