Left panel: top view of the two observers (at the bottom) from above the plane containing the observers and the planet host star. As the planet (empty circle) moves in its orbit, it will appear to transit (here the first contact is shown) at slightly different times for the two observers. Right panel: a view along the orbital plane of the planet from infinity. The two observers (filled circles) are on a line that is inclined at an angle l relative to the orbital plane. The left panel view was taken from a position illustrated by the arrow.