Timelapse: Anticrepuscular Rays at Monument Valley

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:

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

See more of his images here.

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Astrophoto: Curtain of Crepuscular Rays at Dawn

Prolific astrophotographer and Australian astronomer Joseph Brimacombe captured this beautiful wide-field view of crepuscular rays from the Sun last week. You definitely want to click on this image to see a larger view on Flickr. This image is made of seven frames; three exposures each. Brimacombe was lucky to get this shot; just seven minutes later (see the view here), the spectacular curtain of rays were gone.

The word crepuscular means “relating to twilight,” and these rays occur when objects such as mountain peaks 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 so that sunlight in unshadowed areas can be scattered toward the observer.

Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.

Astrophoto: Double Crepuscular Rays

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I’m not sure how often this happens, but I’ve never seen it before: crepuscular rays on both the west and east horizon at the same time — or crepuscular and anti-crepuscular rays occurring simultaneously. I’m staying out in the wilds of Minnesota this summer, with great views of both horizons and captured these images last evening, June 9, 2012. The word crepuscular means “relating to twilight,” and these rays occur when objects such as mountain peaks 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 so that sunlight in unshadowed areas can be 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.
Anyone else ever seen this before?

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. One of the astronauts on the International Space Station actually captured crepuscular rays from orbit, showing how the rays are actually parallel. You can see that image and the description here.

Below are the two images separately. It was a beautiful evening and a thrilling sight.

Sunset crepuscular rays on the west horizon on June 9, 2012. Credit: Nancy Atkinson
Anti-crepuscular rays on the east horizons on June 9, 2012. Credit: Nancy Atkinson.

Crepuscular Rays Seen From Space

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Seeing crepuscular rays on Earth is a somewhat rare event, as conditions have to be just right at either sunset or sunrise for the Sun’s rays to appear as though they are diverging outward from the Sun. But seeing them from space is even more rare.

This picture taken by an astronaut on the International Space Station provides an unusual viewing perspective from above of crepuscular rays. Why are they parallel in this picture instead of radiating in an outward fashion like they appear to us on Earth? This image shows the true nature of crepuscular rays: they really are parallel!

The word crepuscular means “relating to twilight,” and they occur when objects such as mountain peaks or clouds partially shadow the Sun’s rays, when the Sun is low on the horizon. These rays are visible only when the atmosphere contains enough haze or dust particles so that sunlight in unshadowed areas can be scattered toward the observer.

The light rays are actually parallel, but appear to converge to the Sun due to “perspective,” the same visual effect that makes parallel railroad tracks appear to converge in the distance.

In the images taken from the ISS, the sun was setting to the west (image left) on the Indian subcontinent, and cumulonimbus cloud towers provided the shadowing obstructions. The rays are being projected onto a layer of haze below the clouds.

Here’s an image taken by UT reader Stephano De Rosa of crepuscular rays as seen from a more Earthly perspective:

Astrophoto: Crepuscular Rays by Stefano De Rosa
Crepuscular Rays. Credit: Stefano De Rosa

Sources: NASA Earth Observatory, University of Illinois