Special to CosmicTribune.com, March 18, 2025

Excerpts from weekly Sky&Telescope report.

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.

The waning Moon, approaching last quarter, stands high in the south in early dawn, crossing Scorpius. (The best view of the background stars is before dawn begins, meaning at least 90 or 100 minutes before sunrise.)

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.

  March 17-23: Spring returns, The Sky