Some daily events in the changing sky for December 14 – 22.
Comet Holmes remains high in Perseus, dim but big. Look for it southwest of Alpha Persei. You may need binoculars now that moonlight is returning to the evening sky — or go out and look after the Moon sets. (To find your local moonset time use our online almanac. Make sure the Daylight Saving Time box is unchecked.)
Give your eyes plenty of time to dark-adapt. Although the comet's total brightness has remained remarkably constant for weeks (light curve; scroll down), its widening size means that its surface brightness is decreasing. And this makes it tougher to see through any moonlight or light pollution. See our ongoing article.
Also, another comet is on the way in! Comet 8P/Tuttle is magnitude 8 and brightening more or less on schedule. It should reach 6th magnitude from late December through mid-January. And while Comet Holmes stays stuck in Perseus for months, Comet Tuttle (being much nearer) will move far southward across the evening sky during the same time. See the article and charts in the January Sky & Telescope, page 73, and the brief version online.
Friday, December 14
Saturday, December 15
Sunday, December 16
Monday, December 17
Tuesday, December 18
Wednesday, December 19
Thursday, December 20
Friday, December 21
Saturday, December 22
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 standard is Sky Atlas 2000.0) 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 enchanting though increasingly dated Burnham's Celestial Handbook). Read how to use them effectively.
More beginners' tips: "How to Start Right in Astronomy".
This Week's Planet Roundup
Mercury, Jupiter, and Pluto are "combust": an old astronomical term meaning hidden in the glare of the Sun.
Venus (magnitude –4.1, in Libra) is the bright "Morning Star" in the southeast before and during dawn. Look for Spica, much dimmer, well off to its upper right before daylight gets too bright. Arcturus shines much farther to Venus's upper left.
Mars is passing closer to Earth than it will again until 2016. Blazing bright yellow-orange (magnitude –1.6) in Gemini, Mars rises in twilight and is high up in fine view in the east by mid- to late evening, awaiting your telescope. It shines at its very highest around midnight or 1 a.m. — passing near the zenith, in fact, for observers at mid-northern latitudes. By dawn it's glaring lower in the west.
Although Mars is technically closest to Earth on December 18th, the day-to-day difference is insignificant; the planet appears 15.8 or 15.9 arcseconds in diameter all this week and next. Mars will be at opposition on December 24th. For all about observing Mars with a telescope this season, see the guide and surface-feature map in the November Sky & Telescope, page 66.
Saturn (magnitude +0.6) rises in the east around 10 or 11 p.m. and is highest in the south before dawn. Fainter Regulus (magnitude +1.4) is 9° to Saturn's upper right after they rise, and directly right of it as they fade out in dawn's glow high in the southwest.
Uranus (magnitude 5.9, in Aquarius) is visible in the south-southwest right after dark, high above Fomalhaut.
All descriptions that relate to your horizon or zenith — including the words up, down, right, and left — are written for the world's midnorthern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Standard Time (EST) equals Universal Time (UT, UTC, or GMT) minus 5 hours.
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