Saturday, Dec. 17

Sunday, Dec. 18

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

Tuesday, Dec. 20

Wednesday, Dec. 21

Thursday, Dec. 22

Friday, Dec. 23

Saturday, Dec. 24

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.

Sky & Telescope

Once you get a telescope, to put it to good use you

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."

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

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

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….

To be sure to get the current Sky at a Glance, bookmark this URL:
http://SkyandTelescope.com/observing/ataglance?1=1

If pictures fail to load, refresh the page. If they still fail to load, change the 1 at the end of the URL to any other character and try again.