This Week's Sky at a Glance, March 20 – 29

FRIDAY, MARCH 20

■ Look west in the fading twilight this evening for the eerily thin crescent Moon hanging about 8° above Venus. As shown below. Venus is currently on the far side of its orbit from us; it's 650 times farther from us than the Moon.

On Friday evening the 20th, the thin crescent Moon is almost exactly two days old; on Saturday evening, three days old (for evening time the Americas).

■ Spring begins today in the Northern Hemisphere, fall in the Southern Hemisphere. Earth crosses the March equinox point in its orbit at 10:46 a.m. EDT. At last!

At the equinoxes the Sun rises and sets almost exactly due east and west, almost exactly 12 hours apart.

SATURDAY, MARCH 21

■ Sirius shines brilliantly in the south-southwest after dark. Lower left of it, by about one fist, is the triangle of Aludra, Wezen, and Adhara, counting from left to right. They form Canis Major's tail, rear end, and hind foot, respectively. Or alternatively, the handle and the lower end of the Meat Cleaver.

Just left or upper left of the triangle, forming a 3rd- and 4th-magnitude arc just a bit wider than the triangle is, are the three uppermost stars of the constellation Puppis, the p0op deck (stern) of the giant ancient constellation Argo Navis, the ship of Jason and the Argonauts.

These three are the only stars of Argo that are ever readily visible naked-eye from mid-northern latitudes.

Just 1.5° upper right of the middle of the three, binoculars on a dark night will show the little 6th-magnitude open cluster M93. It's elongated northeast-southwest. See Matt Wedel's Binocular Highlight column and chart in the March Sky & Telescope, page 43. He says that in his big 15x binoculars, the cluster "has a distinct cat's-eye shape."

SUNDAY, MARCH 22

■ After dark, spot the Pleiades about 5° upper left of the waxing crescent Moon, as shown below.

The Moons here are always shown about three times their actual apparent size, and the Pleiades group is shown 1.5 times actual size.

■ On the Moon itself this evening, a small telescope or even binoculars will show that two of the gray lunar maria ("seas") have come into sunlight. Round Mare Crisium is near the lunar limb, and Mare Fecunditatis, more irregular, is farther in from the limb and nearly centered in the crescent's arc.

MONDAY, MARCH 23

■ Now the Moon shines almost midway between Pleiades below it and Beta Tauri over it, as shown above. On the Moon itself the sunrise terminator has unveiled Mare Nectaris, which is a little smaller than Crisium, and part of bigger, sprawly Mare Tranquillitatis. Right between Nectaris and Tranquillitatis, the crater Theophilus stands out starkly on the center of the terminator (for evening time in North America).

■ Spring began just three days ago. On the traditional divide between the winter and spring sky lies the dim constellation Cancer. It's high in the south these evenings, midway between" wintry" Gemini to its west and "springtime" Leo to its east.

Cancer may be dim, but it holds something unique in its middle: the Beehive Star Cluster, M44. The Beehive shows faintly to the naked eye if you have little or no light pollution. It's a bit less than halfway from Pollux in Gemini to Regulus in Leo, as shown below. With binoculars it's pretty easy to spot, even under mediocre sky conditions. Look for a scattered clump of faint little stars, magnitudes 6½ on down.

Use a telescope to hunt out the much smaller, fainter open cluster M67 some 9° south of the Beehive. M67 lies 1.8° due west (right) of 4th-magnitude Alpha Cancri, as shown below.

FACING HIGH SOUTH, 9 PM IN MID-MARCH

The Beehive star cluster M44 is usually easy in binocs. Find it about 40% of the way from Pollux to Regulus and a bit south. This month it's also, more simply, halfway from Jupiter to Regulus.

M67, fainter and about five times more distant but richer in stars, requires a telescope. The stars in M67 can be used to find the limiting magnitude of your telescope or narrow-field photographic setup, using this chart. I've managed to glimpse the mag 14.96 star there with my 12.5-inch reflector at 450x through suburban light pollution.

TUESDAY, MARCH 24

■ Now that it's spring Orion has already tilted southwestward by nightfall, with his three-star belt roughly horizontal. Now the belt remains nearly horizontal from when it's high at dusk all the way until it sets due west around 11 or midnight.

WEDNESDAY, MARCH 25

■ First-quarter Moon (exact at 3:18 p.m. EDT). The Moon shines high in the south during dusk, forming an irregular four-sided pattern with Jupiter, Pollux and Castor as shown below. (The scene twists clockwise as evening grows late.)

Another month, and another two Moon-Jupiter-Pollux-Castor quadrilaterals take shape high in the evening sky.

THURSDAY, MARCH 26

■ Castor and Pollux shine near the Moon this evening; bright Jupiter is nearby. Pollux is slightly the brighter of the two Gemini "twins."

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 should show it easily even through tonight's moonlight and/or a fair amount of light pollution. But know what to expect: In typical binoculars it's spread across most of the field of view. As for its shape, it's that thing outlined near bottom center two illustrations above.

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

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

FRIDAY, MARCH 27

■ The signature fall-and-winter constellation Cassiopeia retreats down after dark. Look for it fairly low in the north-northwest. It's standing roughly on end (its brighter end).

But for skywatchers at mid-northern latitudes and farther north, Cassiopeia is circumpolar: never going away completely. By 1 or 2 a.m. daylight-saving time it will be at its lowest due north, lying like a W that's not quite horizontal.

Unless you're too far south. Then it's below the north horizon.

SATURDAY, MARCH 28

■ The huge, bright Winter Hexagon is still in view early after dark, filling the sky to the southwest and west.

Start with brilliant Sirius in the southwest, the Hexagon's lower left corner. High above Sirius is Procyon. From there look higher to the upper right for Pollux and Castor (they're lined up nearly horizontal, with bright Jupiter trying to steal their show). Next go lower right from Castor to 2nd-magnitude Menkalinan and then bright Capella, lower left from there to Aldebaran, then lower left to Rigel at the bottom of Orion, and back to Sirius.

The Hexagon is somewhat distended. But if you draw a line through its middle from Capella to Sirius, the "Hexagon" is fairly symmetric with respect to that long axis.

The Hexagon encompasses almost all of the bright "winter" stars.

SUNDAY, MARCH 29

■ This is the time of year when the dim Little Dipper juts toward the right from Polaris (the Little Dipper's handle-end) during evening. The much brighter Big Dipper curls high above it, "dumping water" into it. They do the reverse water dump in the fall.

Mercury and Mars are deep in the sunrise glare.

Venus, bright at magnitude –3.9, gleams low in twilight, a little less low each week. Look for it due west as twilight fades. Forty minutes after sunset it will still be almost a fist at arm's length above horizontal. Venus sets near twilight's end.

Jupiter is bright and easy, nearly overhead when you face south as the stars come out. Jupiter shines at magnitude –2.3, making it the brightest point in the night sky. It soon shifts to the very high southwest, then moves lower as the evening grows late. It sets around 2 or 3 a.m. on the west-northwest horizon.

In a telescope Jupiter is 40 arcseconds wide. It's shrinking and fading as Earth pulls farther ahead of it in our faster orbit around the Sun.

Jupiter with Io and its shadow, imaged by Raul Cantemir from his backyard in Darmstadt, Germany, at 18:22 UT March 3rd using a 16-inch Newtonian reflector. North is up.

Even a small telescope can show, during good seeing, that the North Equatorial Belt is slightly darker and narrower than the South Equatorial Belt. Note the small dark red oval in the NEB's north edge, at nearly the same longitude as a similar-sized white oval in the latitude of the South South Temperate Belt.

Saturn is hidden behind the glare of the Sun.

Uranus (magnitude 5.8 in Taurus, 4° SSW of the Pleiades) is still fairly high in the west at the end of twilight. At high power in a telescope it's a tiny but non-stellar dot, 3.5 arcseconds wide. You'll need a detailed finder chart to identify it among similar-looking faint stars, such as the chart in last November's Sky & Telescope, page 49.

Neptune is behind the glare of the Sun.

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 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 want 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.

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and hundreds of telescopic galaxies, star clusters, and nebulae among them. Shown here is the Jumbo Edition, which is in hard covers and enlarged for easier reading in the dark by red flashlight. Sample charts. More about the current editions.

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 Deep-Sky Atlas (with 201,000+ stars to magnitude 9.5 and 14,000 deep-sky objects selected to be detectable by eye in very large amateur telescopes), and Uranometria 2000.0 (332,000 stars to mag 9.75, and 10,300 deep-sky objects).

Read How to Use a Star Chart with a Telescope. It applies just as much to electronic charts on your phone or tablet — which many observers find handier and more versatile, if sometimes less well designed and contextualized, than charts on paper.

You'll also want a good deep-sky guidebook. A beloved old classic is the three-volume Burnham's Celestial Handbook. It was my bedside reading for years. 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? Well, I used to say this:

"Not for beginners, I don't think, unless you prefer spending your time getting finicky technology to work rather than learning how to explore through the sky yourself. 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.' "

But, things change. The technology has continued to improve and become more user-friendly — particularly with software that can now recognize any star field to determine exactly where the telescope is pointed — finally bypassing all aiming imperfections in the mount, tripod, gears, bearings and other mechanics, or in the user's skill in setting up.

The latest revolution is the rise of small, imaging-only "smartscopes." These take advantage of not only today's pointing technology, but also the vastly better capabilities of imaging chips and image processing compared to the human retina and visual cortex. The most sophisticated image stacking and processing can also come built right in. The result is decent deep-sky imaging from shockingly small, low-priced units. The image may be viewable on your phone or computer as it builds up in real time. Some can directly enable contributions to citizen-science projects.

Smartscopes are changing the hobby at the entry level. For more on this revolution see Richard Wright's "The Rise of the Smart Telescopes" in the November 2025 Sky & Telescope. And read the magazine's review of this especially small one.

If you get a larger, more conventional computerized scope that you can look through, 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).

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

"Truly, whoever can make you believe absurdities can make you commit atrocities."
            — Voltaire, 1765

View Original Article