We’ve all seen crepuscular rays, or sunrays, converging on the sun. They appear as pillars of sunlight, all meeting at a single point, streaming up from the horizon or down through gaps in clouds. Next time you see them … turn around. You may get a glimpse of the more elusive anticrepuscular rays.
Tips for seeing anticrepuscular rays
To see anticrepuscular rays, you need to turn your back on the sunset. These rays appear to converge toward the antisolar point – that is, the point on the sky opposite the sun. If you want to see them, remember these three tips:
1. When you’re gazing at a beautiful sunset and see crepuscular rays, remember to look behind you to see if there are also anticrepuscular rays.
2. Look carefully, and wait a few minutes to see if they appear over time. Remember that anticrepuscular rays are generally fainter and more elusive than crepuscular rays.
3. You can see them at sunset, but you also can see them at sunrise. Just turn your back on the sun in either situation.
Like crepuscular rays, they are parallel shafts of sunlight from holes in the clouds, and their apparently odd directions are a perspective effect. Think of a long straight road; it converges toward the horizon, but turn around and it also converges to the opposite horizon. Crepuscular and anticrepuscular rays behave in the same way.
Anticrepuscular rays are not rare, but they must be sought carefully. When ordinary crepuscular rays are visible, turn around and search for their opposite numbers.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.
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