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This Week's Sky at a Glance

Some daily events in the changing sky for Sept. 30 – Oct. 8

by Alan M. MacRobert

The M101 supernova is fading and reddening. Supernova 2011fe, which erupted in the nearby galaxy M101 more than a month ago, peaked at about magnitude 9.9 in early and mid-September and is now fading; it was about 11.0 on the evening of October 2nd. It's also turning much deeper orange-red. See an up-to-date light curve.

It's still within visual reach of a 6-inch scope. Although it looks like an ordinary star, it's at least 1,000 times more distant than any other star that's visible in amateur telescopes from northern latitudes. See our article, The M101 Supernova Shines On.

Goodbye to Scorpius for this year
Use binoculars for the faint stars in bright twilight.
Sky & Telescope diagram

Friday, Sept. 30

  • During twilight look far left of the Moon for Antares, as shown above.

    Pre-dawn binocular target!
    Mars is high in the east before the first light of dawn. Use binoculars or a telescope to see the Beehive star cluster far, far behind it. (The 10° scale bar is about the width of your fist held at arm's length.)
    Sky & Telescope diagram
  • Once Mars is up in the early-morning hours Saturday morning, binoculars or a telescope will show that it's passing through the Beehive Star Cluster, M44 in Cancer, as shown here. Mars remains near the Beehive all week.

    Saturday, Oct. 1

  • In twilight, look southwest for the crescent Moon. Can you see Antares twinkling a few degrees beneath it?

    Sunday, Oct. 2

  • Don't miss Mira shining at its unusually bright maximum! It's showing off not far from Jupiter in the evening sky, outshining even Alpha Ceti. Use the finder chart at lower right. See our article for more details.

    Monday, Oct. 3

  • First-quarter Moon (exact at 11:15 p.m. Eastern Daylight Time). The Moon hangs above the Sagittarius Teapot after dark.

    Sky chart for Mira
    Use this chart to locate Mira well to Jupiter's lower right.
    Sky & Telescope diagram
    Tuesday, Oct. 4

  • Jupiter's moon Io casts its tiny black shadow on Jupiter tonight from 11:05 p.m. to 1:17 a.m. EDT. Io itself crosses Jupiter from 11:44 p.m. to 1:52 p.m. EDT. Meanwhile, Jupiter's Great Red Spot transits the planet's central meridian during all of this, around 12:16 a.m. EDT. For timetables of all of Jupiter's satellite events and Red Spot transits this month, see the October Sky & Telescope, page 54.

    Wednesday, Oct. 5

  • Look a little above or upper right of the Moon this evening for Alpha and Beta Capricorni. Binoculars easily reveal Alpha as a wide, yellow double star. Beta (nearer to the Moon) is also a double, but its closer, unequal components are harder to resolve.

    Thursday, Oct. 6

  • Jupiter's Red Spot transits around 1:54 a.m. Friday morning EDT (10:54 p.m. Thursday evening PDT).

    Friday, Oct. 7

  • Look high in the east this evening, far left of the Moon, for the Great Square of Pegasus. It's balancing on one corner. Your fist at arm's length probably just fits inside it.

    Saturday, Oct. 8

  • The Draconid (Giacobinid) meteor shower may put on an intense burst of activity during good observing hours for Europe or possibly elsewhere. Various predictions put one or more outbursts between about 17:00 and 20:30 Universal Time (GMT). The shower's radiant is near the head of Draco, but the meteors themselves can flash into view anywhere in the sky. Unfortunately, the light of the waxing gibbous Moon will obscure all but the brightest of them. See the October Sky & Telescope, page 53.




    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 Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger and deeper 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, 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 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."




    This Week's Planet Roundup

    Mars on Sept. 13, 2011
    With a diameter of only 5 arcseconds, Mars certainly isn't much to look at in a telescope by eye. But stacked-video imaging can work magic. On the morning of September 13th, 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; note the north polar cloud hood at bottom. The brighter, sharper North Polar Cap should be emerging into view as the cloud hood clears off in coming weeks. The large, darkest diagonal mark near top is Mare Cimmerium. Near the center of the disk, bright Elysium is surrounded by dark features

    S&T: Sean Walker
    The Sun is displaying a spot group large enough to see with no magnification, just a safe solar filter. This is Active Region 1302, which could flare and send coronal mass ejections toward Earth at any time. A second spot on the Sun's disk is also visible with more difficulty.

    Mercury is hidden in the glare of the Sun.

    Venus (magnitude –3.9) is just above the horizon a little left of due west if you look 15 or 20 minutes after sunset. Binoculars help. With binoculars, you can also try for vastly fainter and more difficult Saturn just to Venus's upper right on Friday the 30th, and farther to Venus's right after that.

    If you spot Venus, you'll be one of a select few to pick it up this early in its apparition — compared to the billions of people who will see it as the Evening Star blazing high in twilight in the coming months.

    Mars (magnitude +1.3, in Cancer) rises around 2 a.m. daylight-saving time. By the beginning of dawn it's in good view high in the east, well below Castor and Pollux. Well to the right of Mars is Procyon. Farther lower right of Procyon shines bright Sirius. In a telescope, Mars is a tiny blob only 5 arcseconds wide.

    Jupiter on Sept. 19, 2011
    Io and darker Callisto were just east of Jupiter when S&T's Sean Walker imaged the scene on the morning of September 19th. South is up. Note the reddish Oval BA, "Red Spot Junior," just past the central meridian in the South Temperate Belt. Walker made this stacked-video image with the same telescope and setup as for the Mars image above.
    S&T: Sean Walker
    Jupiter (magnitude –2.8, in southern Aries) rises in the east-northeast around the end of twilight and blazes brightly in the eastern sky during evening hours. Look above it for the stars of Aries and closer below it for the head of Cetus, rather dim. (And don't miss Mira, now unusually bright, to the right of the head of Cetus! See our article, Observe Mira, the Amazing Star.)

    Jupiter shines highest well after midnight, making this the best time to examine it with a telescope. It's already a big 48 arcseconds wide as it nears its October 28th opposition. See our guide to observing Jupiter.

    Uranus (magnitude 5.7, in Pisces) and Neptune (magnitude 7.8, in Aquarius) are well placed in the south and southeast by mid- to late 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 Daylight Time (EDT) equals Universal Time (also known as UT, UTC, or GMT) minus 4 hours.

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

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