Panels from top to bottom: observed (LCO) and synthetic (LCC) light-curves of DQ Vel obtained by analysing photometric observations; final O–C residuals between the observed and optimum synthetic light curves; fluxes of donor, gainer and of the accretion disc, normalised to the donor flux at phase 0.25; the views of the optimal model at orbital phases 0.25, 0.50 and 0.75, obtained with parameters estimated by the light curve analysis.