Timelapse: Anticrepuscular Rays at Monument Valley

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Astrophotograher

César Cantú

from Mexico is visiting Utah and captured an incredible timelapse of the view at sunset along with the formation of anti-crepuscular rays -- a spectacular optical phenomena where light rays scattered by dust and haze appear on the horizon opposite to the setting Sun.

The word crepuscular means "relating to twilight," and these rays occur when objects such as hills or clouds partially shadow the Sun's rays, usually when the Sun is low on the horizon. These rays are visible only when the atmosphere contains enough haze or dust particles and in just the right conditions, sunlight is scattered toward the observer.

Then occasionally, light rays scattered by dust and haze sometimes appear on "antisolar" point, (the horizon opposite to the setting Sun). These rays, called anti-crepuscular rays, originate at the Sun, cross over the sky to the opposite horizon, and appear to converge toward the antisolar point.

For both crepuscular and anti-crepsucular, the light rays are actually parallel, but appear to converge to the horizon due to "perspective," the same visual effect that makes parallel railroad tracks appear to converge in the distance.

Above is an image I took a few years ago when I captured both crepuscular and anti-crepuscular rays at the same time.

You can read about that here.

Here's a a great night sky shot of Monument Valley from César:

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Monument Valley in Utah under the starry night sky on May 27, 2014. Credit and copyright: César Cantú.[/caption]

See more of his images here.

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Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com