Antisolar point

The antisolar point is the abstract point on the celestial sphere directly opposite the Sun from an observer's perspective.[1] This means that the antisolar point lies above the horizon when the Sun is below it, and vice versa. On a sunny day, the antisolar point can be easily found; it is located within the shadow of the observer's head. Like the zenith and nadir, the antisolar point is not fixed in three-dimensional space, but is defined relative to the observer. Each observer has an antisolar point that moves as the observer changes position.

A rainbow has 42° centred around the antisolar point, which always coincides with the shadow of the observers eye/camera, seen here at the bottom of the frame.

Centred on the antisolar point, this photo features various antisolar/subhorizon haloes, as viewed from a plane.

The antisolar point forms the geometric center of several optical phenomena, including subhorizon haloes, rainbows,[2] glories,[3] the Brocken spectre, and heiligenschein. Occasionally, around sunset or sunrise, anticrepuscular rays appear to converge toward the antisolar point near the horizon.[4] However, this is an optical illusion caused by perspective; in reality, the "rays" (i.e. bands of shadow) run near-parallel to each other.[5]

Also around the antisolar point, the gegenschein is often visible in a moonless night sky away from city lights, arising from the backscatter of sunlight by interplanetary dust. In astronomy, the full Moon or a planet in opposition lies near the antisolar point. During a total lunar eclipse, the full Moon enters the umbra of Earth's shadow, which the planet casts onto its atmosphere, into space, and toward the antisolar point.