to be known much more accurately ($\Delta P_{\rm orb}/P_{\rm orb}= \Delta \phi P_{\rm orb}/
T \sim 10^{-5}$ day with $T\approx90$ days and an error on the phase set by the exposure time of $\Delta \phi=0.01$). [ Furthermore, the 0.1708 day modulation is probably related to superhumps so that the orbital period can be expected to be close to this value with an uncertainty of a few percent. We tried several different orbital periods around 0.17 day but this had no significant impact on the maps. ]{} The reconstructed trailed profiles and corresponding velocity maps are shown in Fig. \[fig:prof\] and Fig. \[fig:map\] respectively.

Each pixel on the projected Doppler map corresponds to an S-wave in the trailed spectra. The binary components are located on the y-axis of the map at positions corresponding to their semi-amplitude velocities $(v_x,v_y)=(0,-K_1)$ for the primary and $(0,K_2)$ for the companion (indicated by crosses). However, since the orbital reference phase is arbitrary (here we chose $t_0=$51654.420 in MJD), the map can be rotated in any fashion around the velocity origin. The secondary position, the ballistic gas stream trajectory and the corresponding Keplerian velocity at the location of the stream shown on Fig. \[fig:map\] result from particular 