Sky at a Glance | October 10th, 2008

By: Alan MacRobert October 10, 2008 0

Some daily events in the changing sky for October 10 – 18.

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.

Sky & Telescope diagram

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

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

Sunday, October 12

The Dumbbell Nebula, M27, is the brightest planetary nebula in the sky as seen in most instruments. Binoculars usually show it fairly easily. Read about it and use the chart in "Binocular Highlight" in the October Sky & Telescope, page 50.

Monday, October 13

Shortly after dark at this time of year, Deneb crosses nearly straight overhead (for skywatchers at mid-northern latitudes). West of Deneb shines brighter Vega.

Tuesday, October 14

Full Hunter's Moon (exact at 4:02 p.m. EDT).

Wednesday, October 15

The large asteroid 2 Pallas, magnitude 7.3, is 17 arcminutes east of the 2.8-magnitude star Beta Leporis during the predawn hours Thursday morning. At high power, watch for its very gradual motion with respect to the background stars. (Thanks to David Likuski for the tip.)

Thursday, October 16

Early Friday morning, telescope users in western North America can watch the waning gibbous Moon crossing the Pleiades. Stars will disappear on the Moon's bright limb and reappear from behind its narrow dark limb. Of the six brightest Pleiads, only Maia gets occulted for most viewers. Local predictions.

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 1:37 a.m. Friday morning EDT; 10:37 p.m. Thursday evening PDT. 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.)

Mercury is brightening day by day. Look for it low in the dawn far below Saturn.

Sky & Telescope diagram

Friday, October 17

For the next two weeks, little Mercury has its best dawn apparition of 2008 for skywatchers at mid-northern latitudes. Look for it low above the horizon due east (far below Saturn) as dawn brightens.

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.)

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).

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 emerges into view low in the dawn this week, getting higher and brighter day by day. Look for it above the eastern horizon, far below Saturn, about 45 to 30 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.)

Venus (magnitude –3.8) is gradually becoming more prominent after sunset. Look for it above the west-southwest horizon in twilight, about 40 to 60 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.

Christopher Go

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 Sagittarius Teapot and below 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 sinking 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.

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.