Anticrepuscular rays are similar to crepuscular rays

Crepuscular rays

Crepuscular rays , in atmospheric optics, are rays of sunlight that appear to radiate from a single point in the sky. These rays, which stream through gaps in clouds or between other objects, are columns of sunlit air separated by darker cloud-shadowed regions...

, but seen opposite the sun in the sky. Anticrepuscular rays are near-parallel, but appear to converge at the antisolar point

Antisolar point

The antisolar point is the imaginary point on the celestial sphere exactly opposite the Sun. It is where anticrepuscular rays appear to converge, and on a moonless night away from city lights, it is often possible to see the gegenschein there. The apex of a rainbow will also form roughly 42...

 because of linear perspective. Anticrepuscular rays are most frequently visible near sunrise

Sunrise

Sunrise is the instant at which the upper edge of the Sun appears above the horizon in the east. Sunrise should not be confused with dawn, which is the point at which the sky begins to lighten, some time before the sun itself appears, ending twilight...

 or sunset

Sunset

Sunset or sundown is the daily disappearance of the Sun below the horizon in the west as a result of Earth's rotation.The time of sunset is defined in astronomy as the moment the trailing edge of the Sun's disk disappears below the horizon in the west...

. Crepuscular rays are usually much brighter than anticrepuscular rays. This is because for crepuscular rays, seen on the same side of the sky as the sun, the atmospheric light scattering and making them visible is taking place at small angles (see Mie theory

Mie theory

The Mie solution to Maxwell's equations describes the scattering of electromagnetic radiation by a sphere...

).

Although anticrepuscular rays appear to converge onto a point opposite the sun, the convergence is actually an illusion. The rays are in fact (almost) parallel, and the apparent convergence is to the vanishing point

Vanishing point

A vanishing point is a point in a perspective drawing to which parallel lines not parallel to the image plane appear to converge. The number and placement of the vanishing points determines which perspective technique is being used...

 at infinity.

External links

• Atmospheric optics: anticrepuscular rays
• Images of anticrepuscular rays at Astronomy Picture of the Day site (copyrighted images):
  • Image of anticrepuscular rays in Colorado taken by John Britton
  • A particularly vivid image taken by Daniel Herron of Woodstock, GA