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This Week’s Sky at a Glance, February 12 – 20

Friday, February 12

• The sky's biggest well-known asterism (informal star pattern) is the Winter Hexagon. It fills the heavens toward the east and south these evenings. Start with brilliant Sirius at its bottom. Going clockwise from there, march through Procyon, Pollux and Castor, Beta Aurigae and Capella near the zenith, Aldebaran over and down to Capella's lower right, down to Rigel in Orion's foot, and back to Sirius.

Saturday, February 13

• Orion is now high in the south-southeast right after dark. Left of it is Gemini, headed by Castor and Pollux at far left. The stick-figure Twins are still lying on their sides. Well below their legs is bright Procyon in little Canis Minor: the doglet whose top is barely seen in profile in a dark sky. He's vertical at twilight's end. Procyon marks his rump.

Sunday, February 14

• First-quarter Moon for Valentine's Evening (exactly first-quarter at 2:46 a.m. Monday morning EST). Right after dark you'll find the canted Moon shining under the Pleiades, and lower right of Aldebaran and the Hyades.

The February Moon is always in Taurus as it waxes away from first quarter.

Monday, February 15

• This evening the Moon is in the Hyades for North Americans. It creeps along the Hyades's southern arm, with its dark limb occulting 4th-magnitude and fainter stars one by one.

Then comes Aldebaran. By the time the Moon reaches Aldebaran only the West Coast will still have a view, and even there the Moon will be low in the west on its way to setting. The dark limb snaps up Aldebaran at 1:05 a.m. PST for Los Angeles, 1:03 a.m. for the San Francisco area, and around 1:10 a.m. for Portland. From Seattle, the Moon barely misses it.

Tuesday, February 16

• After dusk, the Moon shines above Orion, left of orange Aldebaran, and below Beta Tauri (El Nath), the brighter of Taurus's two horn-tips.

• Jupiter's big, slow moon Ganymede casts its relatively prominent shadow onto Jupiter tonight, from 10:57 p.m. to 2:18 a.m. EST. Ganymede itself crosses Jupiter from 12:58 to 4:06 a.m. EST. Meanwhile, Jupiter's Great Red Spot transits the planet's central meridian around 2:36 a.m. EST. Subtract three hours from these times to get PST.

Wednesday, February 17

• When, precisely, do you see this evening's high gibbous Moon standing exactly over bright Sirius far below? Around 7:50 p.m.? That means you live near your time zone's standard meridian if you're in North America.

The waxing gibbous Moon crossing the Gemini twins. By 9 p.m., Canis Minor just below is diagonal.

Thursday, February 18

• The Moon this evening shines in Gemini, straight above Procyon at nightfall, then upper right of it later as shown here. Jupiter climbs the sky low in the east. The Moon and Jupiter are currently about 60° apart. In five days the Moon will close this gap to shine right next to the bright planet.

• Algol shines at its minimum light, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 10:50 p.m. EST.

Friday, February 19

• This evening the waxing gibbous Moon shines below Castor and Pollux. They don't quite point to it. . . yet. Keep an eye on them as you stay up late. The Moon creeps ever eastward against the stars, and very late tonight (for North America) it aligns with them perfectly.

Saturday, February 20

• Capella crosses highest overhead, and Rigel stands highest in the south, around 7 or 8 p.m. now depending on where you live east or west in your time zone. Capella is at declination +46°, so it passes exactly through your zenith if you're at latitude 46° north: Portland, Oregon; Montreal; northern Italy.

Another, slightly lesser star-pair also transits the meridian in tandem just ten minutes later: Bellatrix (Gamma Orionis) and El Nath (Beta Tauri).

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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.

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but it's less than one per square degree on the sky. Also plotted are many hundreds of telescopic galaxies, star clusters, and nebulae. Shown is the new Jumbo Edition for easier reading in the night. Click image for larger view.

Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or new Jumbo Edition), which shows stars to magnitude 7.6.

Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5, nearly three times as many. Next up, once you know your way around, is 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, or the bigger Night Sky Observer's Guide by Kepple and Sanner.

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."

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This Week's Planet Roundup

All week, Mercury remains 4° lower left of Venus low in the dawn. Binoculars help.

Just how red can the Red Spot get? It's at least as strongly colored this season as at any time in living memory, and it's pretty easy in a 3-inch scope when its side of Jupiter faces Earth. Christopher Go in the Philippines took this stacked-video image with a 14-inch scope on January 12th.

Mercury (still magnitude –0.1) is gradually sinking lower in the southeast before dawn. Look for it 4° lower left of bright Venus.

Venus (magnitude –3.9) is also gradually getting lower in the southeast during dawn.

Mars (magnitude +0.6, in the center of Libra), rises around midnight or 1 a.m. and glows yellow-orange in the south as dawn begins. In a telescope it's still just 7.5 arcseconds in diameter. Notice its gibbous shape; Mars was at western quadrature (90° west of the Sun) just last week.

Mars will appear more than twice as large, 18.6 arcseconds in diameter, when closest to Earth come late May and early June.

Jupiter (magnitude –2.4, between Leo and Virgo) rises in the east around 7 or 8 p.m. and shines highest in the south around 1 or 2 a.m. By dawn it's getting low in the west-southwest.

Saturn (magnitude +0.5, in southern Ophiuchus) rises around 2 or 3 a.m. and is fairly well up in the south-southeast by the beginning of dawn. Spot Antares 8° to its lower right. Mars glows three times as far to Saturn's upper right.

Uranus (magnitude +5.9, in Pisces) is still in the west right after dark.

Neptune (magnitude +8.0, in Aquarius) is getting lost in the sunset.

Planet Nine (probably fainter than magnitude 22, and probably not in the zodiac) seems fairly likely to be out there, but it could be anywhere along a wide sheaf of orbits inclined roughly 30° to the ecliptic. And it's most likely to be near its aphelion, hundreds or even 1,000 a.u. away.

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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 Standard Time (EST) is Universal Time (UT, UTC, or GMT) minus 5 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