Sky at a Glance | December 16th, 2011

By: Alan MacRobert December 16, 2011 0

Friday, Dec. 16

Venus is easy to spot in the southwest during twilight this week. It's getting a little higher every day. And look far off to its left in the south for Fomalhaut, much less bright.

The waning Moon rises around 11 or midnight tonight, with Mars to its left and Regulus higher above it.

Saturday, Dec. 17

Last-quarter Moon (exact at 7:48 p.m. EST). The Moon rises in the east around the middle of the night tonight. Above it are Mars and, higher, Regulus and the Sickle of Leo.

Sunday, Dec. 18

Before and during dawn Monday morning, Saturn and Spica shine more or less left of the Moon, as shown below.

As daybreak approaches, the waning Moon guides the way to Spica and Saturn on Monday and Tuesday mornings, December 19 and 20. They're amid constellations that will shine in the evening sky come spring. (The Moon symbols are positioned for viewers in the middle of North America.)

Sky & Telescope diagram

Monday, Dec. 19

Before dawn Tuesday morning, look above the waning moon for Saturn and Spica, as shown above.

Tuesday, Dec. 20

Wintry Orion is up in the southeast after dinnertime and higher later in the evening. Introduce it to someone! The bright, fire-colored star marking Orion's left corner is Betelgeuse, a prototype red supergiant. The bright star forming Orion's right corner is white Rigel. Midway between them is Orion's three-star Belt, nearly vertical.

Wednesday, Dec. 21

Longest night of the year (in the Northern Hemisphere). Winter begins at the solstice: at 12:30 a.m. on the 22nd EST, 9:30 p.m. on the 21st PST. This is when the Sun reaches its farthest south of the year and begins its six-month return northward. Happy Yule.

The waning crescent Moon points the way to Mercury as dawn brightens on Wednesday and Thursday mornings, December 21 and 22. Can you still find the hairline Moon on the 23rd?

Alan MacRobert

If you continue your Yule celebrations all the way till dawn Thursday morning, go out as day finally begins to break, look low in the southeast, and find Mercury lower left of the waning crescent Moon, as shown here. Farther down below, can you spot Antares yet?

Thursday, Dec. 22

In the evening at this time of year, the Great Square of Pegasus balances on one corner high in the west. The vast Andromeda-Pegasus constellation complex runs all the way from near the zenith (Andromeda's foot) down through the Great Square (Pegasus's body) and almost to the western horizon (Pegasus's nose).

Friday, Dec. 23

Vega, the "Summer Star," still shines brightly in the northwest early these evenings. To Vega's upper left, the Northern Cross in Cygnus is swinging around on its way to planting itself upright on the northwest horizon — which it now does around 9 p.m. (as seen from mid-northern latitudes).

Saturday, Dec. 24

Christmas star: On this date every year, you can go out around 8 p.m., spot Orion well up in the southeast, and look down below it for bright Sirius on the rise. When Sirius is low it often twinkles vigorously with vivid, flashing colors, an effect that's especially visible in binoculars. All stars do this, but Sirius is so bright that the effect is especially pronounced.

New Moon (exact at 1:06 p.m. EST).

Want to become a better amateur astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential magazine of astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

Sky Atlas 2000.0 (the color Deluxe Edition is shown here) plots 81,312 stars to magnitude 8.5. That includes most of the stars that you can see in a good finderscope, and typically one or two stars that will fall within a 50× telescope's field of view wherever you point. About 2,700 deep-sky objects to hunt are plotted among the stars.

Alan MacRobert

Once you get a telescope, to put it to good use you must have a detailed, large-scale sky atlas (set of charts). The standards are the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts effectively.

You'll also want a good deep-sky guidebook, such as Sue French's new Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the classic if dated Burnham's Celestial Handbook.

Can a computerized telescope replace charts? I don't think so — not for beginners, anyway, and especially not on mounts that are less than top-quality mechanically. As Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."

This Week's Planet Roundup

On the morning of December 12th, Mars was 7.7 arcseconds wide and quite gibbous. "The red planet continues its approach each day," writes S&T's Sean Walker. "Note the broken dark ring within the North Polar Cap." Above center is the Aurorae Sinus / Tithonius Lacus region; at lower left is Mare Acidalium.

Although this stacked video image shows far more than you're likely to see in any telescope visually, the North Polar Cap and its bordering dark areas are becoming more visually apparent. South is up. S&T's Sean Walker took this image with a 12.5-inch Newtonian reflector and a DMK21AU618 video camera.

S&T: Sean Walker

Mercury (about magnitude –0.3) is having an excellent apparition in the dawn. About an hour before your local sunrise, look for it low above the southeast horizon, very far lower left of the Saturn-Spica pair.

As dawn brightens, you can also look for fainter Antares beginning to emerge about 7° below or lower right of Mercury.

Venus (magnitude –3.9) shines as the “Evening Star” in the southwest during twilight. It’s getting a little higher every week, heading into a grand apparition high in the evening sky this winter and much of the spring (for the Northern Hemisphere).

Mars (magnitude +0.5, at the hind leg of Leo) rises around 11 p.m. below Regulus and the Sickle of Leo. It's highest in the south before the first light of dawn, with Regulus now to its right. In a telescope Mars is a small blob 8 arcseconds wide.

Jupiter (magnitude –2.7, at the Aries-Pisces border) blazes high in the southeast after dusk and a little higher in the south around 8 p.m. It sets around 2 or 3 a.m. In a telescope Jupiter appears 45 arcseconds wide; see our observing guide.

Jupiter's Great Red Spot (GRS) had just crossed the Jupiter's central meridian when Christopher Go in the Philippines took this world-class image with a 14-inch scope at 11:04 UT December 19th. System II longitude 176° was on the central meridian. South is up. "The wake of the GRS is very complex," Go writes, "while the halo of the GRS is dark."

Christopher Go

Saturn (magnitude +0.7) rises around 2 or 3 a.m. and glows in the southeast well before dawn. Spica, similar in brightness at magnitude +1.0, is 5° or 6° to Saturn's right. Brighter Arcturus shines far to their upper left.

Uranus (magnitude 5.8, near the Circlet of Pisces) is high in the south right after dark.

Neptune (magnitude 7.9, at the Aquarius-Capricornus border) is getting low in the southwest right after dark. Use our printable finder charts for Uranus and Neptune, or see the September Sky & Telescope, page 53.

All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Standard Time (EST) equals Universal Time (also known as UT, UTC, or GMT) minus 5 hours.

With Saturn emerging into good view before dawn, imagers are starting to go after it. On November 28th, Tomio Akutsu in the low-latitude Philippines took this shot with a 14-inch scope when Saturn was 30° high. South is up. Note the irregular white band at the latitude of the North North Temperate Zone. He writes, "I think Saturn's north phenomenon is stlll going on" — referring to the great white outbreak that began there one year ago.

Tomio Akutsu

Like This Week's Sky at a Glance? Watch our new weekly SkyWeek TV short, now playing on PBS!

NEW BOOK: Sue French's DEEP-SKY WONDERS! This big, long-awaited observing guide by Sky & Telescope's Sue French is available from Shop at Sky. Hefty and lavishly illustrated, it contains Sue’s 100 favorite sky tours (25 per season, with telescopic finder charts) from her 11 years of writing the Celestial Sampler and Deep-Sky Wonders columns for S&T. You know you want it for the holidays….

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