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This Week's Sky at a Glance, March 21 – 30

FRIDAY, MARCH 21

■ The evening is moonless, and the southern constellation Puppis, backgrounded by the winter Milky Way, is now, for a brief while, at its highest shortly after dark. Puppis is the stern (poop deck) of the legendary Greek ship Argo. The three 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. They make a dim arc just a bit wider than that showy triangle.

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 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 upward.

SUNDAY, MARCH 23

■ Draw a line from Castor through Pollux, follow it farther on 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 on by another 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.

MONDAY, MARCH 24

■ Many binocular observers check in on the 5th-magnitude open cluster M41 just 4° due south of Sirius. But how many then look the other way from Sirius for the open cluster M50? It's 10° north-northeast from Sirius, dimmer, smaller and more subtle than M41.

Find it by sweeping from Sirius first to Theta Canis Majoris, the 4th-magnitude pointy nose of the Big Dog's stick figure, then on again nearly as far in the same direction and just a touch to the left. M50 is not exactly easy, but it's there. I can spot it without too much difficulty using 10x50 binoculars through moderate suburban light pollution. Use averted vision!

If you're trying under difficult conditions, get more detailed guidance using the Pocket Sky Atlas, chart 27. The more exactly you know the spot to examine for a difficult deep-sky object, the more likely you are to be able to detect it. And, take time. Keep at it.

M50 is about 2,900 light-years from us; M41 is about 2,300.

TUESDAY, MARCH 25

■ 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 26

■ The Big Dipper glitters softly high in the northeast these evenings, standing on its handle and tipping leftward. You probably know that the two stars forming the front of the Dipper's bowl (currently on top) are the Pointers; they point to Polaris, currently to their lower left.

And, you may know that if you follow the curve of the Dipper's handle out and around by a little more than a Dipper length, you'll arc to Arcturus, now climbing in the east.

But did you know that if you follow the Pointers backward the opposite way, you'll land in Leo? Go four or five fists at arm's length.

Draw a line diagonally across the Dipper's bowl from where the handle is attached, continue far on, and you'll go to Gemini (about four fists).

And look at the two stars forming the open top of the Dipper's bowl. Follow this line past the bowl's lip far across the sky, and you cruise to Capella (about five fists).

THURSDAY, MARCH 27

■ Now that it's spring, have you met the Leo Triplet? Three fine spiral galaxies, magnitudes 9 to 10, fit into a 1° eyepiece view in the hind leg of Leo. Two are Messier objects for your life list. See Ken Hewett-White's Suburban Stargazer article, finder chart, and pix in the March Sky & Telescope, page 55.

FRIDAY, MARCH 28

■ If you're in the northeastern US or eastern Canada, find those old eclipse glasses, and/or mount a safe solar filter on the front of your scope, and set an alarm for tomorrow morning's sunrise partial solar eclipse! See next entry.

A partial solar eclipse is seen as the Sun rises behind the Delaware Breakwater Lighthouse on June 10, 2021, at Lewes Beach in Delaware. NASA/Aubrey Gemignani

SATURDAY, MARCH 29

■ A partial eclipse of the Sun happens for northeastern North America, Greenland, Iceland, and most of Europe. For most the northeastern US and the Canadian Maritimes, the eclipse will already be under way at sunrise. Use Xavier Jubier's interactive map to find your own exact times, the maximum obscuration and magnitude of the eclipse at your location, the Sun's altitude, and other circumstances. Times are given in Universal Time.

For instance: At New York City the eclipse is already diminishing when the Sun rises at 6:44 a.m. EDT, with 27% of its surface being obscured at that time. The last trace of the eclipse ends 21 minutes later when the Sun is still a mere 3° above the east horizon. So be on a high rooftop or a shoreline with a flat eastern view.

Boston has it better. The Sun is 57% obscured when it rises at 6:32 a.m. EDT, and it attains 6° altitude by the time the last of the partial eclipse slips away at 7:08 a.m.

At Halifax, maximum eclipse will happen 16 minutes after sunrise, when the Moon will cover 85% of the Sun's surface with the Sun just 2° up.

Also see Bob King's article Sunrise Solar Eclipse on March 29th for Eastern North America, with timetable.

Map of partial solar eclipse, March 29, 2025

SUNDAY, MARCH 30

■ The two biggest generally recognized open star clusters in the sky are the Hyades behind Aldebaran and the Coma Berenices Star Cluster, which is now wheeling up high in the eastern spring sky. The Coma Star Cluster appears about the size of a ping-pong ball held at arm's length. But it's very sparse and dim.

Do you know where to find it? Here's the trick: Look 40% of the way from Denebola, the tail star of Leo, to Alkaid, the end of the Big Dipper's handle and the tail of Ursa Major. Tail of the Lion to tail of the Bear.

In a really dark sky the Coma Star Cluster is a definite dim glow, with its brightest specks forming an upside-down Y. Through poorer skies, it just about fills a binocular's view with somewhat more stars than usual.

This Week's Planet Roundup

Mercury is out of sight in the glare of the Sun. It's at inferior conjunction on March 24th, passing 3.2° north of the Sun.

Venus, by coincidence, is at inferior conjunction just two days earlier, on March 22nd, passing a wide 8.4° north of the Sun.

Venus cusp extensions

Mars (about magnitude +0.2, near the heads of Gemini) comes into view in twilight as a steady orange spark very high toward the south, almost overhead. 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 make is changing faster now, as Mars appears to accelerate away from the end of its retrograde loop. The three dots are on their way to forming a straight line on April 10th.

For telescope users, Mars has shrunk to 8½ arcseconds in diameter and is plainly gibbous (91% sunlit). Best of luck making out 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.

Mars on March 13, 2025

Jupiter shines bright white (magnitude –2.2) high in the southwest at dusk, in Taurus 40° lower right of Mars along the ecliptic. Below Jupiter shines Aldebaran. Above it are Beta and Zeta Tauri. Farther to Jupiter's lower right, you'll find the Pleiades.

Later in the evening Jupiter moves down toward the west. It sets in the west-northwest around 1 a.m. daylight-saving time.

In a telescope Jupiter is about 37 arcseconds wide, small for Jupiter, as Earth pulls far ahead of it in our faster orbit around the Sun. For timetables of the doings of its Galilean moons, see the March Sky & Telescope, page 51.

Jupiter and Io on March 16, 2025

Saturn and Neptune, like Mercury and Venus, are hidden in the glare of the Sun.

Uranus, magnitude 5.8 on the Taurus-Aries border, is still fairly well up in the southwest right after dark, about 7° 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.

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.

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.

Pocket Sky Atlas cover, Jumbo edition

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.

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.

"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