Skywatch for the week of December 7, 2020
Mon Dec 7, 2020 SUNRISE, SUNSET, AND SEASONS
We speak of the sunrise in the east and sunset in the west, but there are only two times during the year when this occurs – at the beginning of spring and at the beginning of autumn. After the spring equinox, the sun rises to the north of east and sets to the north of west, and after the autumnal equinox, the sun rises to the south of east and sets to the south of west. In the summer, the sun’s path across the sky is long and high, the daylight period is longer than the night, and the weather turns warm. In the fall and in the spring, the sun’s path is lower in the sky than it was in summer. The period of daylight and dark is roughly equal, and the air is cooler than in summer, but not so cold as in winter. Lastly, at winter’s beginning, the sun’s path is very short and low; the daylight period is short, the night is long. Air temperatures drop quite a bit during this time, and the weather turns cold.
Tue Dec 8, 2020 BUYING A TELESCOPE FOR CHRISTMAS
Telescopes are popular as Christmas presents, but you can spend a lot of money on a scope only to be frustrated by its poor performance. To start, I recommend binoculars, which are inexpensive, durable and lightweight. When they’re mounted on a camera tripod, you can aim them like a regular telescope, and the images are right side up. Next I’d suggest looking at a catalog company, such as Orion or Celestron or Televue. These online companies can be found with most search engines. But there’s not much time left if you want a telescope shipped for Christmas. If you go to a local store, reflectors that use mirrors are usually better buys than refractors that use lenses. A good reflector will have a primary mirror that’s at least four inches across, preferably six inches. The telescope eyepieces should be one and a quarter inches in diameter, not the hard to use kind that are just under an inch across. Look for a sturdy scope mount with good clamps - avoid cheap plastic and aluminum parts.
Wed Dec 9, 2020 ORION’S RETURN
An old friend has returned to our sky - the ancient constellation Orion the Hunter. You'll recognize him as he rises out of the east around 8 o’clock tonight: three bright stars close together in a row form the hunter's belt. In Robert Frost's "The Star Splitter," the poet begins by saying, "You know Orion always comes up sideways. Throwing a leg up over our fence of mountains, And rising on his hands, he looks in on me Busy outdoors by lantern-light." Orion does come up sideways, first his left shoulder, the star Bellatrix, and the hunter's knee, the blue-white star Rigel; then the belt stars come up in a line, followed by Orion's right shoulder, the well-known star Betelgeuse, and finally his right leg, the star Saiph. When I was young, I saw Orion, looking just as he does now, as did my grandparents, and their grandparents, and so on back for thousands of years.
Thu Dec 10, 2020 ANNIE JUMP CANNON
Annie Jump Cannon was born in Dover, Delaware on December 11, 1863. She studied astronomy and while at the Harvard Observatory, she developed some of the early star classification systems, which resulted in the basic spectral class system used today – O, B, A, F, G, K and M – with the hottest stars being class O, and the coolest class being M. For decades, astronomy students have learned the order of the spectral classes by this mnemonic: “Oh Be A Fine Girl (or Guy,) Kiss Me.” Since this phrase has probably become politically incorrect, I encourage my students to make up their own way to remember, such as, “On Bobsleds A Frost Gives Ken Migraines,” “Orbit Back And Face Green Killer Martians,”, and of course, “Octopus Bait And Fish Guts Kill Manatees (Yucch.) The G stars are yellow in tint, like our sun; cool M type stars are red, K are orange, G and F stars are yellow to yellow-white, and the O, B and A stars are white to blue-white.
Fri Dec 11, 2020 GEMINID METEORS
For the next couple of nights, the Geminid meteor shower sends us “shooting stars,” which seem to come out of the constellation Gemini. Under clear, dark skies the Geminids usually produce a few dozen meteors each hour. Most meteor showers are best after midnight, but only if the moon is not too overpoweringly bright, which keeps us from seeing all but the brightest meteors. Luckily, the waning crescent moon won’t rise until a couple of hours before sunrise, so we’ve got most of the night to enjoy the Geminids. Now if it’s cloudy, you also won’t be able to see the meteors; but if it’s clear, then find a place that’s away from house and street lights, protect yourself against mosquitoes, dress warmly, take a lounge chair that leans all the way back, and face toward the east. The top of the sky should be about the best area to watch. You won’t need a telescope or binoculars, in fact such things would limit your view.