"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 (18541912)
Some daily events in the changing sky for December 12 20.
Friday, December 12
Saturday, December 13
Sunday, December 14
Monday, December 15
Tuesday, December 16
Wednesday, December 17
Thursday, December 18
Friday, December 19
Saturday, December 20
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 foldout map in each issue of Sky & Telescope, the essential magazine of 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 maps; the standards are Sky Atlas 2000.0 or the smaller Pocket Sky Atlas) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion by Strong and Sinnott, the even more detailed Night Sky Observer's Guide by Kepple and Sanner, or the classic Burnham's Celestial Handbook). Read how to use them effectively.
Can a computerized telescope take their place? 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 and a curious mind." Without these, they note, "the sky never becomes a friendly place."
More beginners' tips: "How to Start Right in Astronomy".
This Week's Planet Roundup
Mercury (magnitude 0.8) is still hidden deep in the glow of sunset early this week. But by about the 18th, try scanning for it in early twilight just above your horizon far to the lower right of Jupiter. Bring binoculars.Venus and Jupiter (magnitudes 4.2 and 2.0 respectively), continue pulling apart after their December 1st conjunction. The gap between them widens by 1° per day. Look southwest during twilight. Jupiter, to the lower right of dazzling Venus, is starting to get pretty low.
In a telescope Venus is small (18 arcseconds wide) and gibbous (65% illuminated). Jupiter is 33″ wide, but it has a much lower surface brightness; being 7 times farther from the Sun, Jupiter is lit only about 1/49 as brightly.
Mars remains hidden in the glare of the Sun.
Saturn (magnitude +1.0, near the Leo-Virgo border) rises around 11 or midnight and shines high in the south by dawn. Don't confuse Saturn with similarly-bright Regulus 22° (about two fist-widths at arm's length) to its upper right after they rise, and directly to its right at dawn.
A telescope will show that Saturn's rings have closed to only 1° from edge on. They'll reach a minimum of 0.8° at the end of December, then start opening again before finally closing to exactly edge-on next September when Saturn will, unfortunately, be in conjunction with the Sun.
Uranus and Neptune (magnitudes 5.8 and 7.9, respectively, in Aquarius and Capricornus) are in the southwest and south right after dark. Use our article and finder charts or the chart in the September Sky & Telescope, page 63.
Pluto is hidden in the glare of the Sun.
All descriptions that relate to your horizon or zenith 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 (known as UT, UTC, or GMT) minus 5 hours.
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