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Season of sky oddities

Daryl Pederson
Daryl Pederson says he captured this shot of an "albino rainbow" while he was out
on his sailboat, making his way through the fog in Alaska's Prince William Sound.

Now that fall has arrived in the Northern Hemisphere, we can look forward to more of those misty, foggy, even icy mornings and evenings. And that's prime time for atmospheric curiosities such as sundogs and halos, sun pillars, moon rings and fogbows.

Fogbows, otherwise known as seadogs or "albino rainbows," are particularly easy to see at this time of year, as evidenced by the selection offered up at SpaceWeather.com.

You do have to know what to look for, however. Rainbows, the showiest kinds of atmospheric displays, are created when raindrops act like tiny prisms. When sunlight shines through the drops, some of that light is broken down into a spectrum of wavelengths and bounced back toward observers. The result is an arc of light displaying, naturally, the colors of the rainbow.

Some rainbows are more colorful than others, however, and one of the reasons for that has to do with the size of the drops. The smaller the drop, the less the light is separated into different colors.  (Here's a demonstration showing how droplet size affects the look of a rainbow.) If you get down to the size of droplets in a cloud bank or fog bank, the light is hardly broken down at all. Instead, the diffracted light is a ghostly white.

It's easy to miss that faint ghost of a rainbow, but if you happen to have the sun on one side and mist on the other, keep an eye out for the effect. That's what photographer and storm chaser Tyler Burg did last month when he scouted out his surroundings on a foggy morning near Pisgah, Iowa.

"These were the first fogbows I've seen, and man, were they bright!" he wrote in his SpaceWeather posting.

Burg, who displays his photos at TonightsSky.org, provided a bit more advice in an e-mail exchange: "Just look opposite the sun at a wall of fog," he told me. "You can't be in the fog, or else it's harder to see. They can occur with any light source. A few mornings after that one I saw some from my headlights. I just walked 50 yards in front of my car, and it just appears out of nowhere. Pretty cool stuff. I've heard you can get them from the moon, and streetlights, too. You just have to be willing to get up early and look."

Tyler Burg / TonightsSky.org
Photographer/storm chaser Tyler Burg took this picture of a fogbow framing a
farmhouse near Pisgah, Iowa, on Aug. 30. Burg's shadow is visible in the
foreground. Check TonightsSky.org to see more of Burg's work.

A fogbow was staring Daryl Pederson in the face while he sailing off Alaska last month. "I was out on my sailboat, making my way through the fog in Prince William Sound, and suddenly an albino rainbow appeared," he told SpaceWeather.

SpaceWeather.com is a great place to find out about atmospheric phenomena as well as other sky shows, ranging from meteor showers to sunspots to the latest crop of auroral displays. But for the definitive rundown on halos and bows, rays and glories, and everything else air and light have to offer, the Atmospheric Optics Web site is the place to go. The site even provides an Optics Picture of the Day, modeled after the long-running Astronomy Picture of the Day.

Submitted to FirstPerson
This bright cloud, spotted from Virginia, was created during an experimental rocket launch Saturday evening. Click on the image for a larger version.

One of the latest additions to the atmospheric menagerie cropped up on Saturday evening when researchers used a rocket launch to create the first-ever artificial night-shining cloud.

Some scientists suspect that night-shining clouds, also known as noctilucent clouds, may be popping up more frequently due to global climate change. A couple of years ago, NASA launched a satellite called AIM (Aeronomy of Ice in the Mesosphere) to study the phenomenon. This Discovery Channel video delves more deeply into mesospheric mysteries.

Another satellite, known as STPSat-1, tracked the vestiges of Saturday night's cloud as it dissipated in the atmosphere. One of our readers shared a picture of the light show - and you'll find still more photos at SpaceWeather, including this particularly spooky view from John A. Blackwell of Exeter, N.H.

This YouTube video tracking the launch and the dispersal of the artificial cloud is scary-cool. And this video clip from WFMZ-TV in Pennsylvania, in which eyewitnesses describe the sight in UFO terms, is just plain scary.

Do you have sky views you'd like to share, or oddities you'd like to ask about? You can upload cool pictures of sky or space phenomena to our FirstPerson inbox, and feel free to send along your questions or observations as a comment below.

Update for 3 p.m. ET Sept. 23: Tyler Burg sent along a very cool demonstration of the car-headlight fogbow effect, conducted just this morning at a lake near his house.

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