Sky at a Glance | February 18th, 2011

By: Alan MacRobert February 18, 2011 0

Friday, February 18

Look for Regulus about a fist-width above the Moon this evening. Regulus marks the bottom-right end of the Sickle pattern in Leo. It's the bottom of the Sickle's handle.

Saturday, February 19

This is the time of year when Orion stands at his highest due south in early evening. Upper right of him is Taurus with orange Aldebaran and, farther on, the Pleiades cluster. Lower left of Orion is Canis Major with bright Sirius.

Late these nights the waning Moon guides the way to Saturn and Spica, while Corvus, the Crow, looks on.

Sky & Telescope diagram

Sunday, February 20

These next two weeks, when there's no moonlight in the sky at the end of twilight, it's a fine time to look for the zodiacal light from mid-northern latitudes if you have a very clear, unpolluted sky. As the last of twilight is fading away, look for a vague but huge, tall, narrow pyramid of pearly light extending up from the western horizon. It slopes to the left, following the ecliptic, with Jupiter near its base. What you're seeing is interplanetary dust near the plane of the solar system, lit by the Sun.

By about 10:30 or 11 p.m. the waning gibbous Moon is well up in the east-southeast. Look left of it for Saturn, and lower left of it for slightly fainter Spica. They're higher by midnight, as shown at right. The three of them cross the sky together for the rest of the night to pose in the southwest at dawn Monday morning, as shown at lower right.

The scene for early risers on Monday morning the 21st.

Sky & Telescope

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Monday, February 21

Sirius transits the meridian of the sky (i.e. is due south) around 8 or 9 p.m. this week, depending on where you live east or west in your time zone. Sirius is the brightest star in all the sky (after the Sun). The second brightest is far-southern Canopus. By coincidence, Canopus and Sirius transit at nearly the same time. If you live at least as far south as Atlanta, Phoenix, or Los Angeles, see if you can spot Canopus just above the south point on your horizon when Sirius is approaching the meridian. (Canopus transits 20 minutes before Sirius.)

Tuesday, February 22

You may know of the fine winter star cluster M41, visible in binoculars about one binocular field south of Sirius. But what about the cluster M50? Follow a line from Sirius to the tip of Canis Major's nose (Theta Canis Majoris), continue nearly as far exactly straight onward, and there you are. M50 is magnitude 5.9, quite a bit fainter than M41's magnitude 4.5.

In the same field with M50 is another, fainter cluster: NGC 2343. It's a tougher catch at magnitude 6.7. For a finder chart and more about these objects, see Gary Seronik's Binocular Highlight column in the February Sky & Telescope, page 45.

Wednesday, February 23

Have you ever done a thorough telescopic explore around the horns of Taurus? Starting with the Crab Nebula, use French's Deep-Sky Wonders column and chart in the February Sky & Telescope page 60.

Thursday, February 24

After the last-quarter Moon rises around 2 or 3 a.m. Friday morning, look to its right for Antares and the head of Scorpius. They're high in the south by dawn, as shown below.

Before and during dawn on the 25th, the Moon hangs with Antares.

Sky & Telescope diagram

Friday, February 25

By 8 or 9 p.m. this week (depending on where you live in your time zone), the Big Dipper has risen to the same height in the northeast as Cassiopeia has descended to in the northwest. Their seasonal dominance is reversing; spring is on the way.

Saturday, February 26

After dinnertime at this time of year, four big carnivore constellations are on the march in a row from northeast to south. They're all seen in profile with their noses pointed up and their feet (if any) to the right: Ursa Major the Great Bear in the northeast (with the Big Dipper as his brightest part), Leo in the east, Hydra the Sea Serpent in the southeast, and Canis Major in the south.

Early Sunday morning the asteroid 38 Leda occults an 8.7-magnitude star at the Virgo-Centaurus border for up to 31 seconds as seen from a track crossing from southern Mexico through Texas to Montana. Path map, finder charts, and other details.

Sky at a Glance is now an iPhone app! Put S&T SkyWeek on your iPhone, iPad, or iPod Touch and get the above listings anytime, anywhere — with interactive sky maps! Tap a button to see the scene described, customized for your location worldwide. From there you can scroll the view all around the sky, zoom in or out, change to any time or date, and turn on animation. Now includes This Week's Planet Roundup below.

Go to Apple's iTunes store from your device and buy S&T SkyWeek — just 99 cents!

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 map in the center of each issue of Sky & Telescope, the essential magazine of astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

Sky Atlas 2000.0 (the color Deluxe Edition is shown here) plots 81,312 stars to magnitude 8.5. That includes most of the stars that you can see in a good finderscope, and typically one or two stars that will fall within a 50× telescope's field of view wherever you point. About 2,700 deep-sky objects to hunt are plotted among the stars.

Alan MacRobert

Once you get a telescope, to put it to good use you must have a detailed, large-scale sky atlas (set of charts). The standards are the Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger and deeper Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts effectively.

You'll also want a good deep-sky guidebook, such as Sky Atlas 2000.0 Companion by Strong and Sinnott, or the more detailed and descriptive Night Sky Observer's Guide by Kepple and Sanner, or the classic if dated Burnham's Celestial Handbook.

Can a computerized telescope take their place? I don't think so — not for beginners, anyway, and especially not on mounts that are less than top-quality mechanically. 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

"Jupiter is getting more difficult now," writes imager Christopher Go in the Philippines. He caught this view of the re-formed South Equatorial Belt (above center) in twilight on February 11th just before Jupiter disappeared behind his building's roof. The Great Red Spot is at left. South is up.

Christopher Go

Mercury, Mars, and Neptune are hidden behind the glare of the Sun.

Venus (magnitude –4.2, in Sagittarius) shines as the "Morning Star" in the southeast just before and during dawn.

Jupiter (magnitude –2.1, at the Pisces-Cetus border) shines brightly in the west at dusk and sets roughly an hour after dark now. Get your telescope on it in late twilight while it's still high. Jupiter has shrunk to only 34 arcseconds wide, but try to keep watch on its South Equatorial Belt re-forming as long as you can.

Saturn (magnitude +0.5, in Virgo) rises around 9 p.m., but it's best seen in a telescope at its highest in the south around 2 or 3 a.m. Spica, slightly fainter, shines 9° below Saturn during evening, and left of it at dawn.

Saturn's new white spot now "looks like a comet," writes Christopher Go. This image exaggerates its contrast, but even visually "it is very distinct" in Go's 11-inch scope. He also noted that the North Equatorial Belt "is red and distinct now." South here is up.

Click for animation of several images spanning 33 minutes of Saturn's rotation. This one was shot at 18:50 UT Feb. 6, 2011, when the System III central-meridian longitude was 50°.

And see an even more awesome Cassini image.

Christopher Go

In a telescope, Saturn's new white spot has spread into a double streak far around the planet, as seen here. Saturn's rings are 10° from edge on. See how many of Saturn's satellites you can identify in your scope using our Saturn's Moons tracker.

Uranus (magnitude 5.9) is about 7° west (lower right) of Jupiter and disappearing into the evening twilight.

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) equals Universal Time (also known as UT, UTC, or GMT) minus 5 hours.

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