anticrepuscular rays

{{Short description|Meteorological optical phenomenon}}

File:Colorado_Anticrepuscular_Rays.jpg

File:Anticrepuscular rays from above.jpg, as seen from an aircraft above the clouded ocean.]]

File:Crepuscular rays over Paranal Observatory, Chile.jpg showing both crepuscular and antisolar rays]]

Anticrepuscular rays, or antisolar rays,{{cite web

|url = http://www.atoptics.co.uk/atoptics/anti1.htm

|title = Anti-solar (anti-crepuscular) rays

|first = Les

|last = Cowley

|work = Atmospheric Optics

|accessdate = March 19, 2015

|mode = cs2

}} are meteorological optical phenomena similar to crepuscular rays, but appear opposite the Sun in the sky. Anticrepuscular rays are essentially parallel, but appear to converge toward the antisolar point, the vanishing point, due to a visual illusion from linear perspective.{{cite book

|pages=124–127

|url=https://books.google.com/books?id=0cpQGHqxQBUC&pg=PA124

|author=John A. Day

|title=The Book of Clouds

|year=2005

|publisher=Sterling Publishing Company, Inc.

|isbn=978-1-4027-2813-6

|mode = cs2

}}{{cite web

|url = http://atoptics.co.uk/fz1113.htm

|title = Antisolar rays

|first = Les

|last = Cowley

|work = Atmospheric Optics

|accessdate = March 19, 2015

|mode = cs2

}}

Anticrepuscular rays are most frequently visible around dawn or dusk. This is because the atmospheric light scattering that makes them visible (backscattering) is larger for low angles to the horizon than most other angles. Anticrepuscular rays are dimmer than crepuscular rays because backscattering is less than forward scattering.

Anticrepuscular rays can be continuous with crepuscular rays, curving across the whole sky in great circles.Lynch, D. K., & Livingston, W. (1995). Color and light in nature. Cambridge: Cambridge University Press.