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EYES TO THE SKY: Heavenly halos with sundogs

Lore has it that the name sundog derives from the sense that the swatch of color is tethered to the sun, like a dog on its master’s leash.
February 22 – March 6, 2016

Between the observer and the drama of the circling stars there lies an intermediate realm of coloured lights which play sometimes gently, sometimes strongly, onto the celestial stage.

— From “Astronomy and the Imagination” by Norman Davidson

Sunrise, May 2015. Photo courtesy of Ron Baer.
Sunrise, May 2015. Photo courtesy of Ron Baer.

Mt. Washington — At the beginning of the month, iridescent aquamarine and violet clouds, which are quite rare, shimmered in my field of view above the westering sun, as described in an earlier column. A curious reader of that column asked, to my delight, “What about sundogs?” A sundog’s brushstroke of red and yellow light, usually seen when the sun is rather low in the sky, is, like all colorful sky phenomena, a surprise gift that once enjoyed becomes indelible in our memory.

Sundogs are also known as parhelia from the Greek para = beside + helios = sun. Although it usually isn’t obvious, the splashes of red and sometimes yellow, green and blue beyond, appear at the edge of a 22 degree ice halo around the sun. Halos are common but not easily seen because of the sun’s brilliance. Norman Davidson says they are most easily seen in April and May, although other observers indicate that they can be seen all year.

Halos appear in our skies far more often than do rainbows. They can be seen on average twice a week in Europe and parts of the United States. The 22 degree radius circular halo and sundogs (parhelia) are the most frequent. Permission granted: ©Les Cowley
Halos appear in our skies far more often than do rainbows. They can be seen on average twice a week
in Europe and parts of the United States. The 22 degree radius circular halo and sundogs (parhelia) are the most frequent. Permission granted: ©Les Cowley

If you don’t just stumble upon parhelia, look for them to the left and right of the sun – without ever looking directly at the sun – by extending your arm with the thumb (right edge of sun) or pinky (left edge) of your open hand placed at the respective outer edge of the sun; this approximates 22 degrees out. Always keep your eyes averted from the sun! Sundogs are easiest seen when the sun is rather low and there are high, thin cirrus clouds, which is when I have seen brilliant as well as faint ones. Lore has it that the name derives from the sense that the swatch of color is tethered to the sun, like a dog on its master’s leash.

Full moon rises in the east tonight, the 22nd, at 5:44 p.m., trailed by the brilliant planet Jupiter, which rises at 6:51 p.m. Sunset is at 5:33 on the opposite horizon.

The dawn and pre-dawn planet extravaganza continues with Jupiter at the western tip of the wide arc that includes the bright star Spica in the southwest, ever brightening Mars in the south, Saturn in the south-southeast and Venus in the east-southeast. With sunrise at 6:30 by month’s end, best look by 5:30 – 5:45 a.m. and take a peak half hour before sunrise for Venus.

Sources & resources

Davidson, Norman. Astronomy and the Imagination, Routledge & Kegan Paul, London, 1985

Superb website for atmospheric optics: https://www.atoptics.co.uk/

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NATURE’S TURN: Turning the corner to spring — a Valentine for Earth

“A thing is right when it tends to preserve the integrity, stability and beauty of the biotic communi-ty.” — Aldo Leopold

NATURE’S TURN: Dynamic winter designs in snow, treetops

The first porcupine in a string of winter squatters and the first to enter right beside the doorstep to my home, this entitled individual even tread onto and then sidled sideways off the edge of the lowest steppingstone to my front door to reach the crawlspace.

EYES TO THE SKY: Shortest day, longest night of the year. Four-planet evenings.

The shortest days, longest nights of the year continue from this first day of winter in the northern hemisphere. Only seconds are gained until the end of December.

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