Going Rogue With Twilight

Are you sick of my talking about twilight? Well, tough. My canning the blue-hour talk is about as likely to happen as Flo marrying that gecko. (Thanks Nancy!)

Twilight at Lake Mattakuskeet

Antitwilight sky over Lake Mattakuskeet in eastern North Carolina. This is an old film shot and I can't remember anything about the settings. Let me know if you'd like for me to make something up.

The colorful glow seen in the western sky after sunset and eastern sky before sunrise is called the twilight arch. If the conditions are right, a really cool atmospheric phenomenon occurs with crepuscular rays shining into the sky above the horizon and into the twilight arch. Crepuscular means “pertaining to twilight,” so the term “crepuscular rays” technically refers to sunrays that occur when the sun is below the horizon. (In popular usage, the term also refers to sunrays occurring during the day.) Crepuscular rays typically occur when the sun is around 15 to 40 minutes below the horizon.

Winter twilight sky above Roan Mountain

The twilight wedge hangs above the snow-covered Roan Mountain Highlands on the North Carolina/Tennessee border. For camera info, see above image.

While the twilight arch and crepuscular rays are lighting up the eastern sky at sunrise or the western sky at sunset, in the opposite direction another phenomenon occurs called the antitwilight arch or twilight wedge. As the sun sets in the west, a blue band appears on the eastern horizon with a pink band above it. The blue portion is Earth’s shadow, while the pink portion is the sky illuminated by the sun. As the sun sinks lower, the blue band rises higher. Between 20 to 30 minutes after sunset, the pink band disappears and the blue becomes indistinguishable from the night sky. The exact opposite occurs in the western sky at dawn.

Twilight at Cape Lookout National Seashore

Antitwilight sky above Shackleford Banks at Cape Lookout National Seashore. Nikon F5 (I think), Nikon 17-35mm f/2.8 lens (good guess), f/16 (wild guess), 10 seconds (who knows?), Fujichrome Velvia 50 film (likely).

In addition to the antitwilight arch, there is another phenomenon called anticrepuscular rays, which occurs opposite the rising or setting sun. Typically very faint and observable only in ideal conditions, anticrepuscular rays are rarely observed. I suspect part of the reason we don’t see them as often is because we usually are directing our attention toward the twilight, not antitwilight, sky.

Anticrepuscular rays above Gatlinburg

Anticrepuscular rays shine in the twilight sky above Gatlinburg, TN. Nikon D800, Nikon 14-24mm f/2.8 lens, f/8, ISO 200, varied shutter speed. This is an HDR blend of 5 different exposures.

I’ve only witnessed anticrepuscular rays a few times, although I may have viewed them many times before I realized what I was seeing. I’ve only captured a couple of decent photos of the phenomena, which I am sharing with you here.

Anticrepuscular rays above Linville Gorge.

Anticrepuscular rays shine in the twilight sky over Linville Gorge in Pisgah National Forest, NC. Nikon D2X, Nikon 12-24mm f/4 lens, f/16, 5 seconds, ISO 100.

Anyone who knows me knows that I am addicted to twilight. They also know that I am more likely than not to eschew the standard establishment. So you can imagine why I love antitwilight and anticrepuscular rays. I get to satisfy my twilight addiction while being anti at the same time!

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