This Week's Sky at a Glance
Some night sky sights for December 13 21
Friday, December 13
Saturday, December 14
Sunday, December 15
Monday, December 16
Tuesday, December 17
Wednesday, December 18
Thursday, December 19
Friday, December 20
To keep up with any and all such events this month worldwide, see "Action at Jupiter" in the December Sky & Telescope, pages 51 and 52.
Saturday, December 21
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 heavy and expensive). 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 is lost in the glare of the rising Sun.
Venus (magnitude –4.9) is the brilliant "Evening Star" in the southwest during and after dusk. It's moving lower now day by day as it wanes to a thinner crescent: from 21% sunlit on December 13th to 14% lit on the 20th. During this time, the crescent enlarges from 41 to 51 arcseconds from horn to horn.
Mars (magnitude 1.1, in the head of Virgo) rises around midnight or 1 a.m. By dawn it's very high in the south, but in a telescope Mars is still very small and gibbous: only 6 arcseconds in diameter. Mars passes 3/4° north of the 3.5-magnitude star Eta Virginis on the 17th and 18th.
Jupiter (magnitude –2.7, in Gemini) rises in the east-northeast around the end of twilight, with Pollux and Castor to its left. It blazes highest around 1 or 2 a.m. In a telescope Jupiter has grown to a big 46 arcseconds wide as it nears its January 5th opposition. See lots about observing Jupiter in the January 2014 Sky & Telescope.
Saturn (magnitude +0.6, in Libra) is in the southeast as dawn begins to brighten. Look for it far to the lower left of Mars and Spica, and far lower right of brighter Arcturus.
Uranus (magnitude 5.8, in Pisces) and Neptune (magnitude 7.9, in Aquarius) are still well placed right after dark in the south and southwest, respectively. 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.
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