Dynamic Hα spectrum from the 2005 data (S1+S2). The individual 1D Hα spectra along the orbital phase are plotted in the rest frame of the K star. Dark green corresponds to deep absorption, while light yellow indicates strong emission. The large amplitude (≈320 km s⁻¹) sine curve is the radial velocity of the white dwarf; the smaller amplitude (≈150 km s⁻¹) sinusoid is the radial velocity of the centre of mass of the binary system. The tick marks on the right indicate the phases of the observations.