Sky at a Glance | December 9th, 2011

Friday, Dec. 9

  • Look lower right of the full Moon for Aldebaran this evening, and higher above Aldebaran for the Pleiades.

    The totally eclipsed Moon of October 27, 2004.
    S&T: Richard Tresch Fienberg
  • A total eclipse of the Moon happens for western North America before dawn Saturday morning. Look for the dim, ruddy eclipsed Moon sinking low in the west-northwest before or during dawn. Seen from Hawaii, Australia, and Japan, the eclipsed Moon hangs high in middle of the night. As seen from much of Asia, it's in the evening sky on the 10th.

    The Moon (in Taurus) is totally within the umbra of Earth’s shadow for 52 minutes, from 14:05 to 14:57 December 10th Universal Time (GMT). The partial stages before and after totality each last for more than an hour.

    Saturday, Dec. 10

  • This evening the Moon shines amid Capella to its upper left, Aldebaran to its upper right, Betelgeuse to its lower right, and Pollux and Castor farther to the Moon’s lower left.

    Sunday, Dec. 11

  • Jupiter's Great Red Spot should cross Jupiter's central meridian around 7:16 p.m. EST. For timetables of all of Jupiter's Red Spot transits and satellite events this month, good worldwide, see "Action at Jupiter" in the December Sky & Telescope, page 60.

    Monday, Dec. 12

  • By mid-evening the waning gibbous Moon is up in the east. It's between Pollux and Castor to its upper left and Procyon to its lower right. Much farther to Procyon's right, and perhaps lower, twinkles brighter Sirius.

    Sky map of Geminid radiant
    The radiant (apparent source point) of the Geminid meteor shower is near Castor, the fainter of the Twin Stars in the constellation Gemini. Not shown here is the bright Moon; it's below Gemini on the evening of the 13th and farther below on the 14th.
    Sky & Telescope illustration

    Tuesday, Dec. 13

  • The annual Geminid meteor shower should be strongest late tonight and tomorrow night. But the light of the waning gibbous Moon will hide all but the brightest meteors.

    The shower's radiant, or perspective point of origin, is near Castor and Pollux above the Moon (which is not plotted here). The meteors can appear anywhere in the sky, but their paths, if traced backward far enough across the sky, would cross the radiant.

    Wednesday, Dec. 14

  • Wintry Orion is up in the east-southeast after dinnertime, and higher in the southeast later in the evening. Introduce it to someone! The bright, fire-colored star marking Orion's left corner is Betelgeuse, a prototype red supergiant. The bright star forming Orion's right corner is white Rigel. Midway between them is Orion's three-star Belt, nearly vertical.

    Thursday, Dec. 15

  • The waning Moon rises in the east late this evening with Regulus to its left or upper left. Mars follows them up an hour later.

  • Jupiter's Great Red Spot transits Jupiter's central meridian around 10:33 p.m. EST (7:33 p.m. PST).

    Friday, Dec. 16

  • The waning Moon rises around 11 or midnight tonight with Mars to its left and Regulus higher above it.

    Saturday, Dec. 17

  • Last-quarter Moon (exact at 7:48 p.m. EST). The Moon rises in the east around the middle of the night tonight. Above it are Mars and, higher, Regulus and the Sickle of Leo.


    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 magazine of astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

    Pocket Sky Atlas
    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
    must have 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 effectively.

    You'll also want a good deep-sky guidebook, such as Sue French's new 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 classic if dated Burnham's Celestial Handbook.

    Can a computerized telescope replace charts? I don't think so — not for beginners, anyway, and especially not on mounts that are less than top-quality mechanically. 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."


    This Week's Planet Roundup

    Mars on Dec. 12, 2011, at 9:05 UT
    On the morning of December 12th, Mars was 7.7 arcseconds wide and quite gibbous. "The red planet continues its approach each day," writes S&T's Sean Walker. "Note the broken dark ring within the North Polar Cap." Above center is the Aurorae Sinus / Tithonius Lacus region; at lower left is Mare Acidalium.


    Although this stacked video image shows far more than you're likely to see in any telescope visually, the North Polar Cap and its bordering dark areas are becoming more visually apparent. South is up. S&T's Sean Walker took this image with a 12.5-inch Newtonian reflector and a DMK21AU618 video camera.

    S&T: Sean Walker

    Mercury emerges into dawn view around December 12th. About 40 minutes before your local sunrise time, look for it low above the east-southeast horizon, very far lower left of the Saturn-Spica pair. Mercury is brightening day by day.

    Venus (magnitude –3.9) shines as the “Evening Star” in the southwest during twilight. It’s getting a little higher every week, on its way to a grand apparition high in the evening sky all this winter and much of the spring (for the Northern Hemisphere).

    Mars (magnitude +0.6, at the hind leg of Leo) rises around 11 p.m. below Regulus and the Sickle of Leo. It's highest in the south by the first light of dawn, with Regulus now to its right. In a telescope Mars is a small blob only 7.5 or 8 arcseconds wide.

    Jupiter (magnitude –2.7, at the Aries-Pisces border) blazes high in the southeast after dusk and highest in the south around 8 or 9 p.m. In a telescope Jupiter appears 46 arcseconds wide. See our guide to observing Jupiter with a telescope.

    Jupiter on Dec. 2, 2011, at 12:01 UT
    Jupiter's Great Red Spot had just crossed the central meridian when Christopher Go in the Philippines took this world-class image at 12:01UT December 2nd with a 14-inch scope. South is up. "Condition was almost perfect this evening except for some clouds." he writes. "These are some of my best images of Jupiter with the GRS. The dark halo around the GRS is also covering the South Tropical Zone. The North Equatorial Belt is narrowing, making the dark ovals prominent."

    Saturn (magnitude +0.8) glows in the southeast well before dawn, with Spica (its near twin for brightness at magnitude +1.0) 5° to its right. Brighter Arcturus shines far to their left or upper left.

    Uranus (magnitude 5.8, near the Circlet of Pisces) and Neptune (magnitude 7.9, at the Aquarius-Capricornus border) are in the south and southwest early in the evening. Use our printable finder chart for both, or see the September Sky & Telescope, page 53.


    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.

    Saturn on Nov. 28, 2011
    With Saturn emerging into good view before dawn, imagers are starting to go after it. On November 28th, Tomio Akutsu in the low-latitude Philippines took this shot with a 14-inch scope when Saturn was 30° high. South is up. Note the irregular white band at the latitude of the North North Temperate Zone. He writes, "I think Saturn's north phenomenon is stlll going on" — referring to the great white outbreak that began there one year ago.
    Tomio Akutsu

    Like This Week's Sky at a Glance? Watch our new SkyWeek TV short, now playing on PBS!


    NEW BOOK: Sue French's DEEP-SKY WONDERS! This big, long-awaited observing guide by Sky & Telescope's Sue French is available from Shop at Sky. Hefty and lavishly illustrated, it contains Sue’s 100 favorite sky tours (25 per season, with telescopic finder charts) from her 11 years of writing the Celestial Sampler and Deep-Sky Wonders columns for S&T. You know you want it for the holidays….


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