Sky at a Glance | January 22nd, 2010

Some daily events in the changing sky for January 22 – 30.

Mars's north polar cap was still dazzlingly prominent, and dark Mare Cimmerium was prominent in the north, when Bill Flanagan of the Houston Astronomical Society took this image on January 22nd. Note the bright patch of clouds in the Elysium area just below center. The central-meridian longitude was 210°. South is up, and celestial east is to the right. Click for more views.


Flanagan used a 14-inch Schmidt-Cassegrain telescope and a Luminera LU-075M video camera. Stacked-video imagery like this, done by a skilled user, can show much more detail on a planet than the eye can see through the same telescope.

Bill Flanagan

Friday, January 22

  • This week Mars, in the eastern evening sky, shines its brightest for the year: magnitude –1.3, just a trace less bright than Sirius (magnitude –1.45), which is far to Mars's right in the southeast.

    Midway between Mars and Sirius, and a little higher, is lesser Procyon. The three form a pattern like the wide roof of a low-peaked house.

    Saturday, January 23

  • First-quarter Moon (exact at 5:53 a.m. EST).

    Sunday, January 24

  • As evening grows late, high in the south shines the Winter Triangle: Procyon, Betelgeuse, and bright Sirius at its bottom. Right now its top points have two big extensions: bright Mars far to the upper left of Procyon, and Aldebaran and the Moon far to the upper right of Betelgeuse.

    Monday, January 25

  • A sign of the advancing season: Sometime between about 10 and 11 p.m., depending on where you live in your time zone, the Big Dipper will have risen to the same height in the northeast as Cassiopeia has sunk in the northwest.

    The Dipper is standing on its handle; the Cassiopeia W is balanced on one end. About midway between them (and a bit higher) is Polaris, the North Star.

    Tuesday, January 26

  • If you draw a big X with one line from Capella to Betelgeuse, and another line from Aldebaran to Castor, the Moon shines near their crossing point this evening.

    Wednesday, January 27

  • Mars is closest to Earth, appearing bigger through a telescope (14.1 arcseconds) than anytime from 2008 until 2012. It remains essentially the same size for another week or two. This is an unfavorable showing as Mars apparitions go, however; Mars reached an apparent diameter of 25.1″ in August 2003 and will be 24.3″ in July 2018.

    Watch the big bright Moon cross Gemini on its way to Mars late this week.

    Thursday, January 28

  • The nearly full Moon this evening is accompanied by Pollux and Castor to its upper left, Procyon to its lower right, and Mars farther to its lower left, as shown above.

    Friday, January 29

  • Mars is at opposition, opposite the Sun in Earth's sky. So is the full Moon next to it! Moreover, the Moon is at perigee, making this the largest and brightest full Moon, by a little bit, of the year. (The Moon is exactly full at 1:18 a.m. Saturday morning EST).

    Saturday, January 30

  • Mars shines above the Moon this evening, by about 1½ fist-widths at arm's length. Much closer to the Moon's lower left, look for Regulus.


    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'll need a detailed, large-scale sky atlas (set of charts; 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 more detailed and descriptive 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? 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 and a curious mind." Without these, "the sky never becomes a friendly place."

    More beginners' tips: "How to Start Right in Astronomy".


    This Week's Planet Roundup

    Mercury is having a good morning apparition. Look for it low in the southeast about an hour before your local sunrise time. Don't confuse it with Antares roughly 30° to its upper right, or Altair a similar distance to Mercury's left or upper left.

    Venus is hidden behind the glare of the Sun.

    Mars on Jan. 27, 2010
    Mars was showing much of its "bland side" when S&T's Sean Walker took this image on the evening of January 26th (at 3:42 January 27th Universal Time). The dark-collared north polar cap was still very prominent. Dark, narrow Mare Sirenum is at top right, and the Solis Lacus complex is at top left. South is up.


    "Lots of clouds this year on Mars, as well as here in New Hampshire!" writes Walker. He used a 14-inch Schmidt-Cassegrain telescope and a DMK21AU04.AS video camera. Stacked-video imagery like this can show detail on a planet much more clearly than the eye can see through the same telescope.

    S&T: Sean Walker

    Mars, fiery bright at magnitude –1.3, shines low in the east-northeast in twilight and higher in the east later in the evening. It's in Cancer, nearly midway between Regulus below it and Pollux and Castor above it. Mars is highest in the south around midnight.

    In a telescope Mars is 14 arcseconds wide, as large as it will become this year. The big, white north polar cap is in fine view, bordered by a very wide dark zone. Identify other surface features using the Mars map and observing guide in the December Sky & Telescope, page 57. Mars is closest to Earth on January 27th, when it will be 14.1 arcseconds wide. It comes to opposition on the 29th.

    Jupiter (magnitude –2.0) shines in the west-southwest in twilight and sets soon after dark.

    Saturn (magnitude +0.8, in Virgo) rises in the east around 10 p.m. and stands highest in the south around 4 a.m. In earliest dawn, trace the huge, horizontal line of Spica, Saturn, Regulus, Mars, and Pollux all the way from high in the south to lower in the west-northwest. In a telescope Saturn's rings are tilted 4.8° from edge-on to us, almost the maximum tilt we'll see until next August.

    Uranus (magnitude 5.9, just south of the Circlet of Pisces) is getting low in the southwest after dusk.

    Neptune is lost in the sunset.

    Pluto is very low in the east-southeast before dawn.

    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 (also known as UT, UTC, World Time, or GMT) minus 5 hours.

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