Sky at a Glance | November 11th, 2011

Low in bright twilight
Use binoculars to try for this lineup not long after sunset. The visibility of objects in bright twilight is exaggerated here.
Friday, Nov. 11

  • Spot Venus low in the southwest in bright twilight, and then little Mercury 2° beneath it. Use binoculars to try for twinkly Antares, even fainter, below Mercury as shown here.

  • Much easier: binoculars show the Pleiades above the bright waning gibbous Moon in the east after dark. Below the Moon, Aldebaran sparkles orange.

    Saturday, Nov. 12

  • Jupiter's satellite Io crosses Jupiter's face from 8:15 to 10:24 p.m. EST, followed by Io's tiny black shadow (easier to see in a telescope) from 8:39 to 10:49 p.m. EST. Meanwhile, Jupiter's Great Red Spot transits the planet's central meridian around 8:21 p.m. EST. (For listings of all Red Spot transits and events among Jupiter's moons this month, visible worldwide, see "The Jupiter Watch" in the November Sky & Telescope, page 54.)

    Sunday, Nov. 13

  • The Great Andromeda Galaxy, M31, crosses near your zenith in mid-evening if you're in the mid-northern latitudes. The exact time (sometime around 9 p.m. this week) depends on how far east or west you are in your time zone. Lie on the ground with binoculars, look straight up, and examine the sky just off Andromeda's upraised knee for a dim little elongated glow among the pinpoint stars.

    To piece out the Andromeda constellation, use the monthly evening sky map in the center of Sky & Telescope. Or, the galaxy is just below the "E" in "Andromeda" on the chart farther below.

  • Io reappears from eclipse out of Jupiter's shadow around 8:08 p.m. Eastern Standard Time. With a small telescope, you can watch it gradually swell into view just off Jupiter's eastern limb.

    Monday, Nov. 14

  • The two brightest points on the eastern side of the sky are Jupiter, high in the southeast, and Capella, in the northeast. Find the midpoint between them, and look just below that for the little Pleiades star cluster. The Pleiades are the size of your fingertip at arm's length.

  • Ganymede, Jupiter's biggest moon, crosses the face of the planet from 7:13 to 8:46 p.m. EST. Then Ganymede's tiny black shadow, easier to see, crosses the planet from 8:50 to 10:45 p.m. EST.

    Tuesday, Nov. 15

  • The two brightest stars in the November evening sky are Vega in the west-northwest and Capella in the northeast. Sometime around 8 p.m. tonight, depending on your location, they will be at precisely the same height. How accurately can you time this event? Welcome to medieval astronomy.

    Wednesday, Nov. 16

  • All star atlases show the loose open cluster M39 in Cygnus, which is high in the west these evenings. But what about the "finger of darkness" nearby: the long dark nebula Barnard 168? "Under good (though not pristine) skies," writes Gary Seronik, even his image-stabilized 10×30 binoculars "suffice to show the dark nebula quite well." It's east of M39, about 3° long, and runs east-west. See his Binocular Highlights column and chart in the November Sky & Telescope, page 45.

    Thursday, Nov. 17

  • The bright eclipsing variable star Algol should be in one of its periodic dimmings, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 10:13 p.m. EST (7:13 p.m. PST). Algol takes several additional hours to fade and to rebrighten. The chart below gives the magnitudes of three stars near Algol. Memorize them, and you can use them forever after to judge Algol's changing brightness.

    Algol Star Map
    Algol (Beta Persei) was the first eclipsing variable star discovered. Good comparison stars are Gamma Andromedae to its west, magnitude 2.1, and Epsilon Persei to its east, magnitude 2.9.

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  • The modest Leonid meteor shower should be most active in the hours before dawn Friday morning. Last-quarter moonlight will interfere somewhat.

    Friday, Nov. 18

  • Last-quarter Moon (exact at 10:09 a.m. EST). The Moon shines near Mars and Regulus this morning and tomorrow morning.

    Saturday, Nov. 19

  • Jupiter's moon Io crosses the face of the planet tonight from 10:00 p.m. to 12:09 a.m. EST, with its tiny black shadow following 34 minutes behind. (Subtract 3 hours to get PST.)


    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).

    Sky Atlas 2000.0 (the color Deluxe Edition is shown here) plots 81,312 stars to magnitude 8.5. That includes most of the stars that you can see in a good finderscope, and typically one or two stars that will fall within a 50× telescope's field of view wherever you point. About 2,700 deep-sky objects to hunt are plotted among the stars.
    Alan MacRobert

    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 Nov. 2, 2011
    With a diameter of only 6 arcseconds, Mars still isn't much to look at in a telescope. But stacked-video imaging can work wonders. On the morning of November 2nd, Sky & Telescope's imaging editor Sean Walker assembled this shot using a 12.5-inch Newtonian reflector at f/44, a DMK 21AU618.AS video camera, and Astrodon RGB filters.


    South is up; the north polar region is at bottom. The Solis Lacus area is near top, foreshortened.

    Alan MacRobert

    Mercury and Venus (magnitudes –0.3 and
    –3.8, respectively) remain 2° or 3° apart just above the southwest horizon in bright twilight. Venus is on top; Mercury, much fainter, is below it. On Friday the 11th look below Mercury to try to spot twinkly Antares, even fainter at magnitude +1.1. Later in the week Mercury moves farther away to Venus's lower right. Bring binoculars or a telescope.

    Mars (magnitude +1.0, in Leo) rises around midnight. It's shining close to Regulus, which is nearly as bright at magnitude +1.3 and slightly blue. By the beginning of dawn they're high in the southeast. On the morning of November 12th Mars and Regulus are just 1½° apart. By the 19th their separation widens to 4°, with Regulus on the upper right.

    In a telescope Mars is a tiny blob only about 6.4 arcseconds wide. Mars is on its way to a poor opposition next March, when it will reach a width of only 13.9 arcseconds. Still, that's more than twice as big as it appears now.

    Jupiter on Nov. 5, 2011
    Io was casting its shadow onto Jupiter's Great Red Spot when S&T's Sean Walker took this image on the evening of November 5th. South is to the upper right. The reddish South Equatorial Belt remains wider (and bicolored) compared to the North Equatorial Belt. Walker used the same imaging setup as for Mars above.
    S&T: Sean Walker

    Jupiter (magnitude –2.9, at the Aries-Pisces border) blazes high in the east at dusk and higher in the southeast to south later in the evening. In a telescope Jupiter still appears a big 49 arcseconds wide. See our guide to observing Jupiter with a telescope.

    Saturn (magnitude +0.8) is low in the east-southeast as dawn begins, a little higher every morning. Spot sparkly Spica (magnitude +1.0) 4½° to its right or lower right. Brighter Arcturus shines far to their left or upper left.

    Uranus (magnitude 5.8, in Pisces) and Neptune (magnitude 7.9, in Aquarius) are well placed in the southern sky 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.


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


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