Friday, December 7
Saturday, December 8
For all of Jupiter's satellite events, as well as all of the Great Red Spot's transit times, get our handy new JupiterMoons app!
Sunday, December 9
Monday, December 10
Tuesday, December 11
Wednesday, December 12
Thursday, December 13
Friday, December 14
Sirius, just 8.6 light-years away, is the brightest star in the night sky. It's also the closest that's ever visible to the unaided eye from mid-northern latitudes.
Saturday, December 15
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 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 the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope effectively.
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 certainly not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability). As Terence Dickinson and Alan Dyer say in their invaluable 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, Venus, and Saturn form a diagonal line in the southeast as dawn begins to brighten. Venus is by far the brightest, at magnitude 3.9. Look well to its upper right for Saturn, magnitude +0.7, and farther on for Spica, magnitude +1.0. Look lower left of Venus for Mercury, magnitude 0.5. Mercury is having its best morning apparition of 2012. This line of four points is lengthening: it grows from 33° to 42° long this week.
And watch the waning crescent Moon step down the line on the mornings of December 9, 10, and 11, as shown above.
Mars (magnitude +1.2, in Sagittarius) remains low in the southwest in evening twilight. In a telescope it's just a tiny blob 4.3 arcseconds in diameter — hardly larger than Uranus!
Jupiter (magnitude 2.8, in Taurus) is just past opposition. As twilight fades it's already glaring low in the east. It climbs to dominate the eastern and southeastern sky through the evening, with orange Aldebaran 5° to its lower right and the Pleiades about twice as far to its upper right. Jupiter is highest in the south around 11 or midnight. In a telescope it's a big 48 arcseconds wide, essentially as large as it ever appears.
Uranus (magnitude 5.8, in Pisces) and Neptune (7.9, in Aquarius) are conveniently placed in the south right after dusk but move lower later. 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) equals Universal Time (also known as UT, UTC, or GMT) minus 5 hours.
Like This Week's Sky at a Glance? Watch our SkyWeek TV short. It's also playing on PBS!
To be sure to get the current Sky at a Glance, bookmark this URL:
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.