Orbit of the compact object and circumstellar disc for LSI+61°303, MWC 148, and MWC 656. Red indicates the disc size in Hα, yellow indicates the disc size in Hβ. The blue circle indicates the size of the mass donor. We have three different cases: the orbit crossing the outer parts of the disc (LSI+61°303), the orbit entering deeply in the disc at periastron (MWC 148), and the orbit at the disc border (MWC 656).