This Week’s Sky at a Glance, October 2 – 10

Venus, Regulus, Mars and Jupiter at dawn in early October 2015

On Saturday morning October 3rd, Mars is still only about halfway from Regulus to Jupiter. Watch Jupiter gradually creeping up toward Mars day by day. (The blue 10° scale is about the width of your fist at arm's length.)

Dawn moon and planets, October 9 to 11, 2015

By Friday morning the 9th, when the waning Moon poses with them, Mars and Jupiter are just 3.6° apart. Their conjunction will come on October 17th and 18th, 0.4° apart — with Venus nearing in!

Friday, October 2

• After dark, look just above the northeast horizon — far below Cassiopeia — for bright Capella on the rise. How soon Capella rises, and how high you'll find it, depend on your latitude. The farther north you are, the sooner and higher.

Saturday, October 3

• By about 11 or midnight, the waning Moon rises in the east-northeast. To its right in the east, Orion is also rising. The first bright star you hit looking to the right from the Moon is Betelgeuse: Orion's orange shoulder.

Sunday, October 4

• Last-quarter Moon (exact at 5:06 p.m. Eastern Daylight Time). The Moon rises around midnight tonight, in Gemini.

Monday, October 5

• Look low in the southeast at nightfall for Fomalhaut coming up. It passes highest in the south about 11 p.m.

Tuesday, October 6

• Vesta, the brightest asteroid, is still magnitude 6.2 a week past its opposition. It's easy in binoculars in western Cetus, especially now that the Moon has gone. Use the finder charts in the September Sky & Telescope, pages 48–49.

Uranus, magnitude 5.7, is also nearby! Finder chart.

Wednesday, October 7

• In early dawn Thursday morning, the crescent Moon, bright Venus, and fainter Regulus form a triangle in the eastern sky, as shown here. Jupiter and fainter Mars are down to their lower left, glowing 4° apart.

Thursday, October 8

• The fickle Draconid meteor shower may or may show up this evening. The shower has occasionally been quite active in recent years. See the October Sky & Telescope, page 48.

• In Friday's early dawn the Moon forms a triangle with Jupiter and Mars, while Venus and Regulus now look on from above.

Friday, October 9

• Now that we're well into October, Deneb is replacing brighter Vega as the zenith star after dark (for skywatchers at mid-northern latitudes). Accordingly, Capricornus has replaced Sagittarius as the most notable constellation down in the south.

Saturday, October 10

• A dawn challenge for Sunday morning: About 30 or 40 minutes before sunrise, scan low with binoculars almost due east for the tiny point of Mercury (magnitude +0.6) close to the thin crescent Moon. Despite appearances, these two worlds are rather similar — except that Mercury is 40% larger in diameter and has twice as much surface gravity.

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Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

This is an outdoor nature hobby. 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 guide to astronomy.

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 telescopic galaxies, star clusters, and nebulae.

Once you get a telescope, to put it to good use you'll 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 once you know your way around, the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.

You'll also want a good deep-sky guidebook, such as Sue French's 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 beloved if dated Burnham's Celestial Handbook.

Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (meaning heavy and expensive). 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

Mercury leaps up into dawn view late this week. By Thursday the 8th, look for it 30 or 40 minutes before sunrise low above the horizon due east, far lower left of Venus, Mars, and Jupiter. That morning it's still only magnitude +1.4, but it's brightening fast.

Venus (magnitude –4.7) blazes high in the east during dawn, the brightest of the morning planets. It rises much earlier, around 3 or 4 a.m. Look for much fainter little Regulus sparkling blue-white nearby. In a telescope, Venus is a brilliant thick crescent.

Faint Mars and bright Jupiter (magnitudes +1.8 and –1.7, respectively) shine lower left of Venus. Mars is above Jupiter, closing in on it day by day.

Saturn (magnitude +0.6, just off the head of Scorpius) sinks away in the southwest in twilight. Don't confuse it with orange Antares twinkling 10° to its left.

Uranus (magnitude +5.7, in Pisces) and Neptune (magnitude +7.8, in Aquarius) are well up in the east and southeast, respectively, by 9 p.m. Finder charts for Uranus and Neptune.

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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) is Universal Time (UT, UTC, or GMT) minus 4 hours.

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“This adventure is made possible by generations of searchers strictly adhering to a simple set of rules. Test ideas by experiments and observations. Build on those ideas that pass the test. Reject the ones that fail. Follow the evidence wherever it leads, and question everything. Accept these terms, and the cosmos is yours.”

— Neil deGrasse Tyson