The reduction of light during a transit is related to the size of the planet relative to the size of the star and the limb darkening parameters of the star, i.e. a measure of how much brighter the center of the star is than the edges or limb of the star. The duration of this transit is related to the distance the planet is from the star and their relative sizes. During a transit, the viewer is detecting light from the star which is not being blocked by the planet and any night-side emission of the planet.

The reduction of light during an occultation is related to the reflectivity of a planet or its albedo, the day-side emission of the planet, and the size of the planet. The duration is again related to the distance the planet is from the star and their relative sizes. The location in time of the occultation is also dependent on the orbit of the planet. If the planet is in a circular orbit the occultation will occur exactly half an orbital period after the transit. If the planet is in a non-circular or eccentric orbit the occultation may come sooner or later and the duration will also change. During an occultation, the observer is only detecting light from the star since the planet is being completely obscured.

Assuming that the star is of constant brightness, any out of transit or occultation fluctuations are caused by the planet. This means that we expect to see a growing amount of light as the planet goes from transit to occultation as we see a larger percentage of the planet’s face being illuminated, i.e. we see more of the day-side of the planet. The day-side is also warmer than the night-side and we should also see more emission. So at any other point in time (not in the transit or the occultation) the observer is detecting light from both the star and the planet day-side and night-side depending on location in the planet’s orbit.