Sky at a Glance | October 17th, 2008

Some daily events in the changing sky for October 17 – November 25.

Looking southwest in bright twilight
All week, Venus is getting higher and easier to spot after sunset. Look for Antares, much fainter, moving in toward Venus from the left. Binoculars will help.

Friday, October 17

  • Venus is starting to come into its own as the "Evening Star" low in the sunset, as shown at right. It outshines Antares, the brightest real star in its vicinity, by a factor of 100 (five magnitudes).

  • From now through late October, little Mercury has its best dawn apparition of 2008 for skywatchers at mid-northern latitudes. Look for it low in the east far below Saturn as dawn brightens, as shown below.

    Saturday, October 18

  • Right around nightfall at this time of year, you'll find Arcturus sparkling low in the west-northwest at the same height above the horizon as Capella is sparkling low in the northeast. Arcturus is sinking lower, and Capella is rising higher. How accurately can you time when they're at exactly the same altitude? (The time will vary depending on where you are in your time zone.)

    Sunday, October 19

  • 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 10:25 p.m. EDT. Algol takes several additional hours to fade and to rebrighten. (For all times of Algol's minima this month, good worldwide, see the October Sky & Telescope, page 68.)

    Looking east in early dawn
    Mercury is up before sunrise and brightening day by day. Look for it low in the dawn, far below Saturn.
  • Jupiter's moon Europa reappears out of eclipse by Jupiter's shadow around 10:43 p.m. Pacific Daylight Time, just east of the planet.

    Monday, October 20

  • The annual Orionid meteor shower should be at its peak between midnight and dawn for the next few mornings, but the waning Moon will brighten the sky. You may see a dozen or so meteors per hour of steady watching before dawn.

    Tuesday, October 21

  • Last-quarter Moon (exact at 7:55 a.m. EDT).

    Wednesday, October 22

  • Mercury is at greatest elongation, 18° west of the Sun in the dawn sky.

  • Algol should be at minimum light for a couple hours centered on 7:14 p.m. EDT.

    Thursday, October 23

  • Jupiter's inner moon Io casts its tiny black shadow onto the planet's face from 8:42 to 10:57 p.m. EDT.

    Looking east in early dawn
    Watch the Moon waning from morning to morning is it passes Saturn and, later, low Mercury. (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.)
    Alan MacRobert
  • Tomorrow morning as dawn begins to brighten, the Moon hangs upper right of Saturn (and below Regulus). Use them to guide your way down to Mercury, as shown at right.

    Friday, October 24

  • During dawn tomorrow, look for Saturn to the upper left of the Moon, as shown here.

    Saturday, October 25

  • Venus is passing 3½ from Antares at dusk. See the illustration under "Venus" below.

  • During dawn tomorrow, Saturn, the Moon, and Mercury form a tall tableau in the eastern sky.


    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).

    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, which brightens from magnitude 0.0 to –0.8 this week, is coming into its best morning apparition of 2008. Look for it low in the east, far below Saturn, about 60 to 45 minutes before sunrise. (You can always find your local sunrise time, and much else, once you put your location into our online almanac. If you're on daylight saving time like most of North America, make sure the Daylight Saving Time box is checked.)

    Near Venus, Can you still see Antares through the sunset afterglow?
    Alan MacRobert
    Venus (magnitude –3.8) is slowly becoming more prominent after sunset. Look for it above the southwest horizon in twilight, about 45 to 60 minutes after sundown. Binoculars hill help you spot Antares to Venus's left or, later in the week, lower left.

    Mars is lost in the sunset.

    Vesta, the brightest asteroid, is easily spottable with binoculars at magnitude 6.5 in the head of Cetus. It gets high late in the evening. Use the finder chart in the November Sky & Telescope, page 67.

    Jupiter (magnitude –2.2, 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 sinking Sagittarius Teapot and below the smaller, dimmer Teaspoon.

    Saturn shines in the east at dawn. Don't confuse it with fainter Regulus higher up. A telescope will show that Saturn's rings have turned nearly edge on; they're currently tilted 2.5° 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) sinks in the southwest after dark.

    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.


    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 this URL to any other character and try again.