This Week’s Sky at a Glance

Friday, December 27

  • Got a new Christmas telescope? Wondering what to do with it? Read this!

    Dawn is now coming its latest of the year. Step out early enough and you can watch the waning Moon passing Saturn and Antares.
    Alan MacRobert
  • In Saturday's cold dawn, Alpha Librae (Zubenelgenubi) shines 1° to 3° lower left of the waning crescent Moon for North America, with Saturn 5° farther on, as shown here. The Moon occults (covers) Alpha Librae for Hawaii; timetable.

  • Yes it's cold out. That's no reason to be cold or to shun the beauties of winter astronomy. Learn to be a toasty winter observer with "Dress for Stargazing Success" in the December Sky & Telescope, page 66.

    Saturday, December 28

  • Very late tonight, tomorrow, and Monday nights, Mars is just 3/4° from Gamma Virginis (Porrima), magnitude 2.7 — a famous close double star for telescopes at high power. Mars and Gamma Vir rise together after midnight and are best seen high in the south before dawn.

    Sunday, December 29

  • Orion's Sword is the dimmer straight line of stars at an angle to Orion's Belt. It's currently to the belt's lower right, as Orion climbs the southeastern evening sky.

    Often you read that the Great Orion Nebula, partway down the sword, looks to the naked eye like a slightly fuzzy star. Well, maybe. To start with you need sharp (or fully corrected) distance vision. You also need a good sky — and light pollution doesn't seem to be the whole story here. On some nights in the suburbs I can see the nebula around the 5th-magnitude stars Theta-1 and Theta-2 Orionis fairly positively. On other nights with the same light pollution, not so much. How about you?

    Monday, December 30

  • When evening twilight turns to night at year's end, the constellation Andromeda is crossing the zenith (for the world's mid-northern latitudes). The Great Andromeda Galaxy passes right through your zenith if you're near latitude 41° north (New York, Denver, Madrid). This happens at 6:05 p.m. tonight if you live at your time zone's standard longitude. If you're east or west of there, as you probably are, the galaxy will transit as much as 30-plus minutes earlier or later, respectively. Lie on your back and look straight up with binoculars for a dim, elongated little glow of fuzzy gray among the pinpoint stars.

    Tuesday, December 31

  • After the New Year's cheering at midnight, step outside into the silent dark. Sirius shines almost due south. Jupiter, even brighter, beams much higher to the south. Orion strides to the upper right of Sirius. Procyon shines to Sirius's upper left, and Leo is climbing the eastern sky.

    Wednesday, January 1

  • New Moon (exact at 6:14 a.m. EST).

  • Extremely Young Moon. Shortly after the Sun sets, in central and western North America you can try to spot what will almost certainly be your personal record-young crescent Moon, perhaps for the rest of your life. An extremely thin trace of the Moon will be almost straight above the sunset point — and conveniently for locating it, 8° to 9° lower right of Venus. And the Moon is at perigee.

    The sighting will probably be impossible from the East Coast, where the Moon will be just 11 hours old and only 7° from the Sun a half hour after sunset. But it might be possible through a telescope in the Central time zone if the air is very clear. It should be possible with binoculars on the West Coast, where the Moon will be approximately 14 hours old and 8.5° from the Sun. Figure its age from the time of new Moon: 11:14 UT (3:14 a.m. Pacific Standard Time).

    Go out early to mark where the Sun sets, then set up your equipment and start watching no more than 15 minutes after sundown. Keep watching for another 25 minutes to catch your window of best visibility, which will depend on your location and atmospheric conditions. For more on this pursuit, see Seeking Thin Crescent Moons.

    Use the waxing Moon to find Venus very low now after sunset. (The Moon, shown three times life size, is positioned as seen from the middle of North America.)
    Alan MacRobert

    Thursday, January 2

  • As twilight starts to fade, look for the thin crescent Moon (24 hours older now, much easier than yesterday) above Venus low in the southwest, as shown at right. Venus too is a (tiny) crescent. The two crescents face almost the same way toward their light source, the Sun. (In parts of western North America a telescope may show the Moon's dark, Earthlit limb occulting Beta Capricorni, but the Moon will be very low and the observation difficult.)

  • The brief Quadrantid meteor shower is predicted to peak around 19h or 20h UT (11 a.m. or noon Pacific Standard Time). This is good timing for the eastern half of Asia but broad daylight in North America. By one prediction, however, the Quads may come a few hours early and be active before dawn for the West Coast.

    Friday, January 3

  • After sunset, look far lower right of the waxing crescent Moon for Venus, dropping lower every day. How much longer can you keep Venus in view? It will reach inferior conjunction, 5° north of the Sun, on January 11th.

    Saturday, January 4

  • Soon after dark Sirius, the Dog Star, rises below Orion, and Procyon, the Little Dog Star, rises to the lower right of bright Jupiter. Which of them comes up first? It's Procyon if you're north of latitude 30° (Tijuana, New Orleans, Jacksonville), and Sirius if you're south of there.

    Hint: "Procyon" means "Before the Dog." That tells you something about where its namers lived.


    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).

    The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but that's less than one star in an entire telescopic field of view, on average. By comparison, Sky Atlas 2000.0 plots 81,312 stars to magnitude 8.5, typically one or two stars per telescopic field. Both atlases include many hundreds of deep-sky targets — galaxies, star clusters, and nebulae — to hunt among the stars.
    Sky & Telescope

    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

    Jupiter on December 26th, imaged in extraordinary detail by Christopher Go in the Philippines. South here is up.

    The Great Red Spot (GRS) is unusually strong orange this season. Note the massive turbulence in the South Equatorial Belt to the spot's following (celestial east) side. Barely following the spot, a tiny new bright-white outbreak has begun. The System II longitude on the central meridian here is 226°; the Red Spot had recently crossed the meridian.


    Mercury is hidden in conjunction with the Sun.

    Venus (about –4.5) is dropping lower in evening twilight every day. Look southwest. Optical aid shows it becoming an ever thinner crescent: from 7% sunlit on December 27th to just 2% lit on January 4th. But it's big! —about 59 arcseconds in diameter. Good binoculars will show its crescent shape in twilight.

    The best time to observe Venus in a telescope is well before sunset. Hide the Sun behind a building so you can't accidentally sweep it into your view. Read our article, See Venus's Thin Crescent. Venus is heading to inferior conjunction with the Sun on January 11th.

    Mars (magnitude +0.8, in Virgo) rises around midnight. It's highest in the south before the first light of dawn. Mars is 3/4° from Gamma Virginis, 2 magnitudes fainter, on the mornings of December 28, 29, and 30. By January 4th it moves nearly 3° away from the star.

    In a telescope Mars is gibbous and still small, not quite 7 arcseconds in diameter.

    Jupiter (magnitude –2.7, in central Gemini) is nearly at its January 5th opposition. So it glares low in the east as twilight fades, then rises higher in the east all evening (with Pollux and Castor to its left and fainter Gamma Geminorum a similar distance to its right). It blazes highest in the middle of the night.

    In a telescope Jupiter is 47 arcseconds wide, as big as you're going to see it. Read up on observing Jupiter in the January Sky & Telescope.

    Saturn (magnitude +0.6, in Libra) is well up the southeast as dawn begins to brighten. Look for it far to the lower left of Mars and Spica, and far below brighter Arcturus.

    Uranus (magnitude 5.8, in Pisces) is high in the south right after dark.

    Neptune (magnitude 7.9, in Aquarius) is getting low in the southwest after dark. 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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