Some daily sky sights among the ever-changing Moon, planets, and stars.
Friday, December 5
The Moon is essentially full this evening and Saturday evening both (it's exactly full at 7:27 a.m. Saturday morning EST.) On Friday evening in the Americas, look for Aldebaran less than about 2° from the Moon. Watch the Moon shift east with respect to it during the night.
Saturday, December 6
By mid-evening the Moon shines high in the east. It's in a starry part of the sky. Aldebaran is now to its upper right. To the Moon's lower right is Aldebaran-colored Betelgeuse. Much farther lower left of the Moon are Castor and Pollux. And high to the Moon's upper left? There's Capella.
Sunday, December 7
Look right of the Moon this evening for Betelgeuse, and farther right for the rest of Orion. Watch far down below the Moon in midevening for Procyon to rise. Then watch equally far below Orion's Belt for brighter Sirius to rise a little later (as seen from the world's mid-northern latitudes).
Monday, December 8
The waning Moon rises by 7 or 7:30. As it climbs higher, look to its left for Pollux and, above Pollux, Castor. To the Moon's lower right, Procyon is on the rise.
Tuesday, December 9
The waning gibbous Moon, now in Cancer, is well up in the east by about 9 p.m. depending on your location. Look to its right for Procyon. Farther to the Moon's upper left are Pollux, and above Pollux, Castor.
Wednesday, December 10
Mid-December is when the dim Little Dipper hangs straight down from Polaris around 9 p.m.
Thursday, December 11
The waning Moon rises in the east by about 10 or 10:30 p.m. tonight, with bright Jupiter shining to its upper left. Fainter Regulus, to their lower left, forms a nearly equilateral triangle with them. The scene at right shows how you'll see them by early dawn Friday morning.
Keep an eye out for early-arriving Geminid meteors! This annual shower should peak late on Saturday and Sunday nights; see below.
Friday, December 12
This is the time of year when, around 8 or 9 p.m., Cassiopeia crosses very high in the north as a flattened letter M. When do you see it lined up perfectly level?
Saturday, December 13
The Geminid meteor shower should be at its strongest late tonight and tomorrow night. Bundle up even more warmly than you think you'll need, find a dark, shadowed site with an open view overhead, lie back in a reclining lawn chair, and watch the stars. Be patient. Under a fairly dark sky you may see a meteor every minute or two. See article, Warm Up with December’s Geminid Meteors.
Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.
This is an outdoor nature hobby; 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 guide to astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).
Once you get a telescope, to put it to good use you'll need 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 once you know your way around, the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.
You'll also want a good deep-sky guidebook, such as Sue French's 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 beloved if dated Burnham's Celestial Handbook.
Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability, which means fairly heavy and expensive). 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
Mercury is hidden in the glare of the Sun.
Venus (magnitude –3.9) is beginning to peek through the glow of sunset. Look for it just above the southwest horizon about 20 minutes after sundown. Binoculars help, and the farther south you live the better. See Bob King's article Venus Finally Comes Out of Hiding.
Mars (magnitude +1.0, in Capricornus) still glows in the southwest during and after twilight. And it still sets around 8 p.m. local time.
Jupiter (magnitude –2.3, in western Leo) rises in the east-northeast around 10 p.m. About 40 minutes later, fainter Regulus (magnitude +1.4) rises below it. By dawn they shine high in the south, with Regulus now to Jupiter's left.
Saturn (magnitude +0.5, in Libra) is emerging into the dawn sky. In early dawn, look for it low in the east-southeast, far below Arcturus and Spica. Binoculars help.
Uranus (magnitude 5.8, in Pisces) and Neptune (magnitude 7.9, in Aquarius) are still well up in the southern sky right after dark. Use binoculars or a small telescope and our finder charts for Uranus and Neptune.
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) is Universal Time (UT, UTC, or GMT) minus 5 hours.
"Science is built up of facts, as a house is with stones. But a collection of facts is no more a science than a heap of stones is a house."
— Henri Poincaré (1854–1912)