Sunset in the east? Rare anticrepuscular rays make it appear so

Weather Blog
Anticrepuscular rays at sunset Thursday

Crepuscular and the opposite, anticrepuscular rays of sunlight were both seen across parts of Central Texas Thursday evening.

Crepuscular rays are beams of sunlight shining through clouds, or from beneath the horizon at sunset. The opposite effect was seen Thursday evening in the Hill Country–rays of light appearing to originate in the east–anticrepuscular rays.

Here’s how the National Weather Service describes them:

Perhaps you have heard of Crepuscular Rays…those rays of sunshine that poke through holes in cloud cover. Did you know there also are Anti-Crepuscular Rays?  This phenomena occurs when low-angled sunlight gets blocked by cloud cover…and would be visible on the opposite horizon.  That is, sunrise rays would be visible in the western sky, or sunset rays in the east.

Here’s how our friends at EarthSky.org explain them:

We’ve all seen crepuscular rays, or sunrays, converging on the sun. They appear as pillars of sunlight, all converging at a single point, streaming up from the horizon or down through gaps in clouds. Next time you see them … turn around.

If you look opposite the direction of the sun, you might catch a glimpse of elusive anticrepuscular rays. These rays appear to converge towards the antisolar point – that is, the point on the sky opposite the sun. If you want to see them, remember these three tips:

1. Look in the direction opposite the sun, next time you see crepuscular rays extending from the horizon.

2. Look carefully. Remember that anticrepuscular rays are fainter and more elusive than crepuscular rays.

3. Watch around sunrise or sunset for anticrepuscular rays. That’s when they are are most frequently visible.

And, from NASA:

What’s happening over the horizon? Although the scene may appear somehow supernatural, nothing more unusual is occurring than a setting Sun and some well placed clouds. Strangely, the actual sunset was occurring in the opposite direction from where the camera was pointing. Pictured above are anticrepuscular rays. To understand them, start by picturing common crepuscular rays that are seen any time that sunlight pours though scattered clouds. Now although sunlight indeed travels along straight lines, the projections of these lines onto the spherical sky are great circles. Therefore, the crepuscular rays from a setting (or rising) sun will appear to re-converge on the other side of the sky. At the anti-solar point 180 degrees around from the Sun, they are referred to as anticrepuscular rays.

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