This Week's Sky at a Glance, March 14 – 23

FRIDAY, MARCH 14

■ The round Moon, less than a day past full, rises in twilight. As it climbs higher after dark, keep watch below it (by about two fists at arm's length) for springtime Spica to rise too. Spica follows about 1½ or 2 hours behind the Moon as they cross the sky.

■ Algol should be at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for about two hours centered on 8:26 p.m. EDT Friday evening.

SATURDAY, MARCH 15

■ The waning Moon rises around the end of twilight. Now Spica will be closer below the Moon once they're both up in view, following only about 15 or 20 minutes behind.

Right of Spica by a fist and a half, look for the four-star pattern of Corvus, the springtime Crow, as illustrated above. About twice that distance left of Spica and the Moon sparkles bright Arcturus.

■ High overhead after dusk, Mars tonight forms a perfect right triangle with Pollux and Castor. Perfect for all practical purposes, that is. The angle at Pollux measures 89.7° (during evening-time for the Americas).

Mars continues to fade; it's down to magnitude +0.1 — still brighter than Pollux, mag 1.1, and Castor, mag 1.6.

SUNDAY, MARCH 16

■ And now the Moon, waning further, rises about an hour after full dark, following Spica this time rather than preceding it. The late moonrise means you can plan for some good deep-sky observing right after nightfall. Be set up and ready to go as soon as twilight ends, in order to catch the window of darkness before the lunar floodlight turns on.

■ For instance: On the traditional divide between the winter and spring sky lies the dim constellation Cancer. It's now very high toward the south-southeast in early evening, between Gemini to its west and Leo to its east.

Cancer holds something unique in its middle: the Beehive Star Cluster, M44. The Beehive shows dimly to the naked eye if you have little or no light pollution. Where to look? The Beehive is a bit less than halfway from Pollux in Gemini to Regulus in Leo. With binoculars it's easy, even under mediocre sky conditions. Look for a scattered swarm of faint little stars, magnitudes 6½ on down.

And use a telescope to hunt out the much smaller, much fainter open cluster M67 some 9° below the Beehive. It's 1.8° due west of 4th-magnitude Alpha Cancri.

MONDAY, MARCH 17

■ Sirius, the Dog Star, the brightest star after the Sun, shines due south crossing the meridian as the first stars come out in the fading twilight. How early can you spot it?

Look next for the stars of Orion about two fists to Sirius's upper right. The brightest of these is Rigel in Orion's leading foot.

Procyon, the Little Dog Star in Canis Minor, shines two fists to Sirius's upper left. Procyon always crosses the meridian 54 minutes after Sirius does. The two Dog Stars form the equilateral Winter Triangle with Betelgeuse, Orion's orange-yellow shoulder.

■ Whenever Procyon transits the meridian, you'll find Pollux and Castor transiting higher up: nearly overhead for mid-northern latitudes. The changing triangle that they've formed with Mars all this winter is no longer quite a right triangle; its angle at Pollux now measures 92.7°, not essentially 90° like two days ago (again, during evening in North America). Is this enough distortion from a proper square corner for you to detect yet by eye?

TUESDAY, MARCH 18

■ This is the time of year when Orion declines in the southwest through the evening, with his Belt turning roughly horizontal. But when will Orion's Belt appear exactly horizontal tonight? That depends mostly on your latitude, and to a lesser degree on where you're located east-west in your time zone.

WEDNESDAY, MARCH 19

■ The waning gibbous Moon rises around 1 a.m. tonight daylight-saving time, in the head of Scorpius. Before and during early dawn Thursday, the Moon and its surrounding stars pose well up in the southeast to south as shown below. You're getting a preview of the summer Scorpion.

THURSDAY, MARCH 20

■ The Pollux corner of the Mars-Pollux-Castor triangle now measures 99.3°, plainly no longer a right angle by eyeball judgment.

■ Spring begins in the Northern Hemisphere at the moment of the equinox, 5:01 a.m. EDT this morning.

FRIDAY, MARCH 21

■ The evening is moonless, and the southern constellation Puppis, weakly highlighted by the winter Milky Way, is now, briefly, at its highest shortly after dark. Puppis is the stern (poop deck) of the legendary Greek ship Argo. The dim, northernmost stars of the stern's stick figure lie less than a fist-width to the left of the bright triangle forming Canis Major's tail and hindquarters.

One of the loveliest offerings of Puppis is the 3rd-magnitude open cluster NGC 2451 way down below those top stars. Find this and other deep-sky sights near it using Matt Wedel's Binocular Highlight article and chart in the March Sky & Telescope, page 43.

And don't wait. NGC 2451 is very low at declination –38°, so find an observing spot with a low view due south and catch it while you can. The farther south you live the better.

■ Last-quarter Moon tonight (it's exactly last-quarter at 7:29 a.m. Saturday morning EDT). Moonrise is around 3 a.m. Saturday morning. Catch the Moon when it's higher just before Saturday's dawn begins, and you can see that it's at the spout of the Sagittarius Teapot, which is sitting level. Incidentally you're seeing the Moon at almost the very farthest south it can ever possibly get, at declination –29½°.

SATURDAY, MARCH 22

■ Arcturus, the "Spring Star," now rises above the east-northeast horizon around the time when the stars come out. How soon can you spot it?

Once Arcturus is nicely up, look for the narrow Kite asterism of Boötes extending two fists to its left. The left end of the Kite is bent slightly up.

SUNDAY, MARCH 23

■ Draw a line from Castor through Pollux, follow it farther out by a big 26° (about 2½ fist-widths at arm's length), and you're at the dim head of Hydra, the Sea Serpent. In a dark sky it's a subtle but distinctive star grouping, about the width of your thumb at arm's length. Binoculars show it easily through light pollution.

Continue that line farther by a fist and a half and you hit Alphard, Hydra's 2nd-magnitude orange heart.

Another way to find the head of Hydra: It's almost midway from Procyon to Regulus.

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This Week's Planet Roundup

Mercury is fast ending its evening apparition. On Friday the 14th it's barely visible just above the due-west horizon in bright twilight, 9° left of Venus. Start looking for it with binoculars 30 or 40 minutes after sunset. Good luck; Mercury is only magnitude 1.3.

Each evening after that it gets even fainter and lower, on its way to inferior conjunction March 24th.

Venus is a couple hundred times brighter at magnitude –4.2. It too is very low in the west in twilight and dropping lower every day. On March 14th Venus sets in late twilight, but by the 17th or 18th it sets while twilight is still bright.

But Venus now shows its most unusual phase in a telescope! It's a hairline crescent just 2% or 1% illuminated. Get your scope on it as early in twilight as you possibly can, before is sinks even deeper into the bad low-altitude seeing.

Better yet, locate Venus telescopically in the blue-sky daylight of late afternoon. Set up your scope someplace where the Sun has already sunk below a hill or a building to your west, so you can't accidently sweep up the Sun in your scope and burn your eye! Sweep slowly and carefully for Venus using the finderscope, or if that doesn't work, by using your lowest-power, widest-field eyepiece.

On March 14th you'll find Venus 15° above the Sun and probably a little to the right depending on your latitude. By March 22nd Venus will be passing a wide 8.4° to the celestial north of the Sun — that is, to the Sun's upper right as seen from our mid-northern latitudes. That's the date it's at inferior conjunction!

And once you pick up Venus with the naked eye, try to detect its crescent shape! See Bob King's Venus Sprints from “Evening Star” to “Morning Star”. As he notes, almost any binoculars will confirm whether you're actually seeing the crescent naked-eye . . . or, for edge cases, maybe just tiny eye aberrations.

Mars (about magnitude +0.1, near the heads of Gemini) comes into view in twilight as a steady orange spark very high toward the south. It continues to fade as it shrinks into the distance.

As darkness deepens, watch for fainter Pollux and Castor (magnitudes 1.1 and 1.6) to emerge near it. The triangle that the three of them make is changing faster now, as Mars appears to accelerate away from the end of its retrograde loop. They form an exact right triangle on March 15th.

For telescope users, Mars has shrunk to 9 arcseconds in diameter and is plainly gibbous (92% sunlit). Best of luck following even its largest surface markings as it dwindles. A Mars map is in the January Sky & Telescope, page 48, and in Bob King's Mars Extravaganza online. To find which side of Mars (i.e. which part of the map) will be facing you at the date and time you'll observe, use our Mars Profiler tool.

Jupiter shines bright white (magnitude –2.2) high in the southwest at dusk, in Taurus 36° lower right of Mars along the ecliptic. Below Jupiter shines orange Aldebaran. Farther to Jupiter's lower right are the Pleiades.

Later in the evening Jupiter moves down toward the west. It sets in the west-northwest around 2 a.m. daylight-saving time.

In a telescope Jupiter is about 38 arcseconds wide, smallish for Jupiter, as Earth far outpaces it in our faster orbit around the Sun. For timetables of the doings of its Galilean moons and the meridian transits of its Great Red Spot, see the March Sky & Telescope, page 50.

Saturn and Neptune are hidden in the background of the Sun.

Uranus, magnitude 5.8 on the Taurus-Aries border, is still fairly high in the southwest right after dark, about 8° below the Pleiades. You'll need a good finder chart to tell it from its similar-looking surrounding stars; see last November's Sky & Telescope, page 49.

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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 and graphics that also depend on longitude (mainly Moon positions) are for North America.

Eastern Daylight Time (EDT) is Universal Time minus 4 hours. UT is also known as UTC, GMT, or Z time.

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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 a more detailed 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.

For the attitude every new amateur astronomer needs, read Jennifer Willis's Modest Expectations Give Rise to Delight.

Once you get a telescope, to put it to good use you'll need a much more detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas, in either the original or Jumbo Edition. Both show all 30,000 stars to magnitude 7.6, and 1,500 deep-sky targets — star clusters, nebulae, and galaxies — to search out among them.

Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many, as well as many more deep-sky objects. It's currently out of print, but maybe you can find one used.

The next up, once you know your way around well, are the even larger Interstellarum atlas (with 201,000+ stars to magnitude 9.5, and 14,000 deep-sky objects selected to be detectable by eye in large amateur telescopes), and Uranometria 2000.0 (332,000 stars to mag 9.75, and 10,300 deep-sky objects). And read How to Use a Star Chart with a Telescope. It applies just as much to charts on your phone or tablet as to charts on paper.

You'll also want a good deep-sky guidebook. A beloved old classic is the three-volume Burnham's Celestial Handbook. An impressive more modern one is the big Night Sky Observer's Guide set (2+ volumes) by Kepple and Sanner. The pinnacle for total astro-geeks is the new Annals of the Deep Sky series, currently at 11 volumes as it works its way forward through the constellations alphabetically. So far it's up to H.

Can computerized telescopes replace charts? Not for beginners I don't think, and not for scopes on mounts and tripods that are less than top-quality mechanically. Unless, that is, you prefer spending your time getting finicky technology to work rather than learning how to explore the sky. 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, "the sky never becomes a friendly place."

If you do get a computerized scope, make sure that its drives can be disengaged so you can swing it around and point it readily by hand when you want to, rather than only slowly by the electric motors (which eat batteries).

However, finding faint telescopic objects the old-fashioned way with charts isn't simple either. Do learn the essential tricks at How to Use a Star Chart with a Telescope.

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Audio sky tour. Out under the evening sky with your
earbuds in place, listen to Kelly Beatty's monthly
podcast tour of the naked-eye heavens above. It's free.

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"The dangers of not thinking clearly are much greater now than ever before. It's not that there's something new in our way of thinking, it's that credulous and confused thinking can be much more lethal in ways it was never before."
            — Carl Sagan, 1996

"Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence."
            — John Adams, 1770

 

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