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 Jupiter tonight from 10:00 p.m. to 12:09 a.m. EST. Io's tiny black shadow follows 34 minutes behind. (Subtract 3 hours to get PST.)

    Sunday, Nov. 20

  • 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 7:02 p.m. EST. Algol takes several additional hours to fade and to rebrighten. Here's a comparison-star chart giving the magnitudes of three stars near Algol; use them to judge its changing brightness.

    Dawn view

    Early risers can watch the waning crescent Moon pass Spica and Saturn. (These scenes are drawn for the middle of North America. European observers: move each Moon symbol a quarter of the way toward the one for the previous date. For clarity, the Moon is shown three times actual size.)

    Sky & Telescope diagram

    Monday, Nov. 21

  • During dawn Monday morning the waning crescent Moon points down to Saturn and Spica, as shown above. On Tuesday morning, the three form a roughly horizontal line.

    Comet Garradd (C/2009 P1) on Nov. 14, 2011

    Comet Garradd has hardly changed appearance in the last few months. Paolo Candy in Italy shot this image on November 14th using an 8-inch scope for a combined 40 minutes of CCD exposures.

    Paolo Candy


    Tuesday, Nov. 22

  • Comet Garradd continues glowing at about magnitude 6.5 as predicted, but it's getting low. Find it in the west with binoculars or a telescope right at the end of twilight. To locate the exact spot to examine, start from the head-star of Hercules (Rasalgethi) using our finder chart online or in the November Sky & Telescope, page 52. In a few weeks Comet Garradd will become too low to view well after sunset but will become more easily visible before dawn.

    Wednesday, Nov. 23

  • These moonless evenings are a fine time to get out the telescope and explore the Veil Nebula and lesser-known deep-sky sights in Cygnus, which is still very high in the west in early evening. See Sue French's "Deep-Sky Wonders" article, charts, and photos in the November Sky & Telescope, page 56.

    Thursday, Nov. 24

  • The Great Square of Pegasus floats highest in the south these evenings. It's somewhat bigger than your fist at arm's length. Its right-hand (west) side points down roughly to Fomalhaut much, much lower in the south. Its left-hand (east) side point down roughly to dimmer Beta Ceti (Diphda), not quite as low.

    Friday, Nov. 25

  • Tonight Jupiter's icy, enigmatic moon Europa crosses onto the face of the planet at 9:45 p.m. EST, then exits at 12:10 a.m. EST. Europa's tiny black shadow crosses Jupiter from 11:08 p.m. to 1:34 a.m. EST.
  • New Moon (exact at 1:10 a.m. on this date EST). The Moon partially eclipses the Sun for Antarctica, Tasmania, and small sections of South Africa and New Zealand.

    View in bright twilight

    The thin Moon pairs with Venus after sunset on Saturday the 26th. You may need binoculars to pick up Mercury; its visibility low in bright twilight is exaggerated here. (These scenes are drawn for the middle of North America. European observers: move each Moon symbol a quarter of the way toward the one for the previous date. For clarity, the Moon is shown three times its actual size.)

    Sky & Telescope diagram


    Saturday, Nov. 26

  • As twilight fades, look low in the southwest for the very thin crescent Moon hanging to the right of Venus — a beautiful sight! Seen from the time zones of the Americas, they're 3° to 5° apart.

    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).

    Once you get a telescope, to put it to good use you 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 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.

    This Week's Planet Roundup

    Mars on Nov. 2, 2011

    With a diameter of just over 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 (about magnitude 0) begins the week nicely visible to the lower right of bright Venus, low in the southwest during twilight. Mercury becomes a little tougher each day, fading and sinking farther away to Venus's lower right.

    Venus (magnitude –3.9) is creeping higher into better view in the southwest during twilight. It's on its way up for a grand, high apparition as the "Evening Star" during and after twilight all this winter (for the Northern Hemisphere).

    Mars (magnitude +0.9, in Leo) rises around midnight. By the beginning of dawn it's high in the south-southeast. It's near Regulus, which is only a little fainter at magnitude +1.3 and slightly blue-white. Mars and Regulus widen from 4° apart on the morning of November 19th to 7½° by the 26th.

    In a telescope Mars is a tiny blob only about 6.7 arcseconds wide. Mars is on its way to opposition next March, when it will reach a width of 13.9 arcseconds.

    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 –2.8, 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 48 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. 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 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.

    To be sure to get the current Sky at a Glance, bookmark this URL:
    http://SkyandTelescope.com/observing/ataglance?1=1

    If pictures fail to load, refresh the page. If they still fail to load, change the 1 at the end of the URL to any other character and try again.

    • About Alan MacRobert

    Alan M. MacRobert became an avid Sky & Telescope subscriber in 1966 at age 14, joined the editorial staff in 1982, and is now a senior contributing editor, semi-retired. He played a role in practically every part of the magazine and the company's other products for more than a generation, both on the amateur-observing side and the science-reporting side. In 1994 a book collection of his observing how-tos and telescopic sky tours was published as Star Hopping for Backyard Astronomers. He has produced This Week's Sky at a Glance online every week since 1989.

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