Difference Between Sun Dogs and Sun Halos: Lovely Oregon Coast Science

Updated Periodically
By Oregon Coast Beach Connection Staff

(Oregon Coast) – One of the more fascinating finds and sights on the Oregon coast are sun dogs, moon dogs, sun halos or moon halos. They are not exclusively viewed on the beaches, but some can be a little less rare out here, and they add a truly heavenly aspect to your beach experience if you’re lucky enough to catch one. (Above: sun dog photo courtesy Tiffany Boothe, Seaside Aquarium).

Sun dogs are part of a larger family of halos that includes the stunning moon halos – which come in many forms. But there’s a difference between sun dogs and halos, whether it’s moon halos or sun halos. Sun dogs are rarer formations where there are two bright spots on either side of the sun (or moon, much more rarely). Like a lens flare effect on a camera. Sun or moon halos are simply giant bright circles around either the sun or moon.

Tiffany Boothe of Seaside Aquarium has acquired some photos of these in the past, seen here.

Sundogs also go by the names sun dog, mock sun or parhelion: their scientific name is parhelia. (At right: photo Oregon Coast Beach Connection - a sun dog at Pacific City).

“Also known as a phantom sun, sun dogs are created by ice crystals in the atmosphere interacting with light,” Boothe said.

They show up as a pair of bright spots on either side of the sun. Often, they are seen with a large, luminous area around the sun as well.

Like many light phenomena associated with the sun – including the Green Flash at sunset on the Oregon coast – refraction is the key. Scientists say sun dogs are caused by ice crystals with a hexagonal shape, sitting high in the atmosphere in very cold air. These act like prisms, bending the light and making interesting, luminous shapes. The taller the sun dog, the more these objects are wobbling as they move through the atmosphere.

They tend to be visible more often when the sun is close to the horizon, and in that lie some interesting tricks of light. The part closest to the sun can be more red, while the parts farther from the sun tend to be more blue or green.

Both halos and sun dogs are created by refraction, meaning the light is passing through the ice crystals are being bent. With halos, light is usually being bent by 22 degrees, but sometimes at 46 degrees.

Moon halos are sometimes at least as stunning, and they are the result of tiny ice crystals lurking high in the sky, usually around 20,000 feet above and existing as thin, wispy clouds. These come in two flavors: a giant, whitish ring around the moon, or a blob of colors surrounding the moon. Both require a thin layer of clouds that does essentially the same thing in terms of refraction that the sun dog does.

Many of the multicolored forms are much smaller, but they seem to have a rainbow full of colors. Amusingly, they can also resemble Pac Man in the sky.

Moon halos like this – and the whitish kinds - often mean rain or snow are coming soon, and they are often the forerunners of storm clouds right behind. More photos of these phenomena below: Oregon Coast Lodgings for this event - Where to eat - Maps - Virtual Tours

MORE PHOTOS BELOW

Above: sun halo photo courtesy Angi Wildt. Below: two incarnations of moon halos.

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