Ultraviolet SED of BF Cyg during its 1990 optical maximum (mid) and the following quiescent phase (bottom). Times of observations are denoted by arrows at the top panel with the light curves. In both cases, the binary was seen from the same position with the hot star in front (orbital phase ϕ ~ 0.6). The dashed and the thin solid line represent the continuum from the nebula and the hot star, respectively. The thick solid line is the model SED. The grey surface marks the Rayleigh attenuated continuum with n_H = 4.8×10²² cm^-2, and strong blended absorptions of the iron curtain are denoted by “i.c.”.