The phase-angle α(φ) as function of orbital phase φ for an orbital inclination of 44.5^° (dashed line), and the resulting contrast curve assuming a Lambertian phase function Φ(α) (solid line). The orbital phase is 0 when the planet is located closest to the observer (i.e. during transit for a planet with an orbital inclination of ~ 90^°). At this moment, the phase angle is maximal and the contrast is minimal because a small part of the day-side of the planet is in view.