Looking Up column: Catching stars on the horizon
I had most of the sky before me; a canopy of stars visible from my so-called deck observatory on the back of my house. So what grabbed my attention? A couple of little patches of sky straight ahead of me on the horizon, peeking between the tree line in the back of the neighbor’s field.
No craning of the neck this time!
Some of you may be graced with a clear, wide-open sky where you can pan the flat horizon all the way around in a circle. You must be living in the middle of a Midwestern ranch, on a mountain top or on a houseboat out at sea! Of course, a lot more people in rural areas are fortunate to have a really low view in the sky in at least one direction, or more than one.
Dodging trees, hills and buildings can be a challenge.
On the other hand, seeing the stars, planets and moon among the tree branches, when empty of leaves, can be very picturesque as one takes an evening stroll.
From the convenience of my backyard deck, I was thrilled to gaze with binoculars at those small gaps. I saw stars!
What was thrilling was looking due south at night, I was seeing a hint of far southern constellations, ones that never fully rise above my horizon at my latitude. These stars are wrapped in an air of mystery, an enticing invitation to want to head far south, the farther the better, as I round the Earth and see the southern stars slide higher and higher in my sky. There is a whole region of sky anyone of us above (or below) the equator can never see.
Using my star atlas, I identified those low stars in the wood line gaps as the brighter stars of the constellation Vela the Sail.
There’s a good chance you northerners (like me) know very little, or maybe nothing, of Vela the Sail!
On trips to Florida and Haiti, I have had chances to see stars of the Southern Cross; Alpha Centauri, the closest star system to our Sun; and a few other constellations and notable stars I can’t see at home. Yet, way below the equator, such wonders as Octans the Octant, Dorado the Swordfish, Mensa the Fly and Telescopium the Telescope await being traced and enjoyed. Folks Downunder may feel the same mystique about the Big Dipper, Little Dipper, Cassiopeia and Camelopardalis the Giraffe, far northern star patterns hidden from them.
Note, our view low to the horizon also means we are looking through a thicker layer of atmosphere. Just like the sun is dimmer and redder at sunset/sunrise, the stars are dimmed at night along the horizon. Light pollution from populated areas past the horizon can create a bright glow low in the sky.
There is also an interesting aspect of the low stars near the horizon. Thanks to the Earth’s atmosphere acting like a lens, the starlight is refracted, and appears a little higher in the sky than it would if we had no air (like on the moon). That means starlight right below our flat horizon is bent and comes into view! Refraction also makes the setting and rising sun and moon distorted.
The atmosphere is most turbulent at low angles, causing a star to “twinkle” and cause poor telescopic views of planets just rising or setting.
Knowing your latitude, with the help of a good star chart you can find the limit of how far down the sky you can see from your home.
Meanwhile, enjoy brilliant Venus in the evening western sky. New moon is on April 22.
Keep looking up at the sky!
Peter Becker is managing editor at The News Eagle in Hawley, Pennsylvania. Notes are welcome at firstname.lastname@example.org. Please mention in what newspaper or website you read this column.