Sky at a Glance | October 3rd, 2008

Some daily events in the changing sky for October 3 – 11.

Looking west in bright twilight
Watch the Moon wax in the west from night to night, passing Venus and fainter Antares. (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.)

Friday, October 3

  • In twilight, look for summery Antares still glimmering barely in view low in the southwest. It's upper left of the crescent Moon, as shown here.

    Saturday, October 4

  • Antares twinkles to the right of the Moon early this evening.

    Sunday, October 5

  • Jupiter's moon Europa emerges out of eclipse by Jupiter's shadow around 8:30 p.m. EDT, just east of the planet. A small telescope will show it gradually swelling into view.

    As the Moon waxes through the week, watch it pass Jupiter and the Sagittarius Teapot. (The blue10° scale is about the size of your fist held at arm's length).
    Alan MacRobert
    Monday, October 6

  • Get a low-power scope onto Venus low in the west-southwest as twilight fades, and look for the wide double star Alpha Librae less than 1° to its north (upper right). This direction is correct at the time of twilight in North America. Venus itself is tiny (13″ wide) and gibbous.

  • Jupiter is the thing shining above the Moon this evening. Jupiter is now at eastern quadrature, 90° east of the Sun.

    Tuesday, October 7

  • First-quarter Moon (exact at 5:04 a.m. EDT). This evening, Jupiter shines to the Moon's right.

    Wednesday, October 8

  • Jupiter's moon Io emerges out of eclipse by Jupiter's shadow around 9:47 p.m. EDT, just east of the planet. A small telescope will show it gradually swelling into view.

    Thursday, October 9

  • Early Friday morning, telescope users along the East Coast from Labrador to Florida can watch for whether the faint asteroid 225 Henrietta will occult (cover) a 10.4-magnitude star near the head of Cetus (not in Monoceros; that was an error). See the October Sky & Telescope, page 68.

    Friday, October 10

  • The red long-period variable star W Lyrae should be about at its peak brightness (8th magnitude) this week. Follow its doings with binoculars or a small telescope and the chart in the October Sky & Telescope, page 67.

    Saturday, October 11

  • Jupiter's moon Ganymede disappears into eclipse by Jupiter's shadow around 9:39 p.m. Pacific Daylight Time, a little east of the planet. A small telescope will show it gradually fading away.


    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 foldout map in 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 it's still less than one per square degree on the sky. Also plotted are many hundreds of good telescopic galaxies, star clusters, and nebulae.
    Sky & Telescope
    Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of maps; 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 even more detailed 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? 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, they wisely say, "the sky never becomes a friendly place."

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



    This Week's Planet Roundup

    Mercury is hidden in the glare of the Sun.

    Venus (magnitude –3.8) is gradually becoming more prominent after sunset. Look for it above the west-southwest horizon in fairly bright twilight, about 45 minutes after sundown.

    Mars is lost in the sunset.

    Even though Earth is pulling away from Jupiter as the season advances, Christopher Go in the Philippines took another of his suberb stacked-video images on September 28th. The Great Red Spot had crossed the central meridian less than an hour earlier; the image was taken at 10:24 UT, when the System II central-meridian longitude was 148°. Note the white rift in the South Equatorial Belt (above center) and the narrower white rift in the narrower North Equatorial Belt. South is up, to match the south-up view in many telescopes.
    Jupiter (magnitude –2.5, in Sagittarius) shines highest in the south-southwest in twilight, and lower in the southwest later, so get your scope on it early. Once night arrives, you'll see that Jupiter is above the Sagittarius Teapot and below the end of the smaller, dimmer Teaspoon.

    Saturn glows in the east at dawn. (Don't confuse it with Regulus higher up.) A telescope will show that Saturn's rings have turned nearly edge on; they're currently tilted 3° to our line of sight and closing. They'll reach a minimum of 0.8° at the end of the year, then start opening again.

    Uranus and Neptune (magnitudes 5.7 and 7.9, respectively, in Aquarius and Capricornus) are in the southeast and south during evening. Use our article and finder charts or the chart in the September Sky & Telescope, page 63.

    Pluto (magnitude 14.0, in the northwestern corner of Sagittarius) is the southwest right after dark. If you've got a big scope and a dark sky, use our article and finder chart.

    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 Daylight Time (EDT) equals Universal Time (known as UT, UTC, or GMT) minus 4 hours.


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