This Week's Sky at a Glance, May 22 – 31

FRIDAY, MAY 22

■ We have a first-quarter Moon both this evening and tomorrow evening. The Moon is exactly first quarter at 7:11 a.m. EDT tomorrow morning, about halfway between the two evenings (for the Americas).

■ Spot 1st-magnitude Regulus just a couple degrees to the Moon's upper left after dark. From Regulus, the Sickle of Leo extends toward the right now, with its cutting edge facing down. It's a little more than a fist at arm's length long.

SATURDAY, MAY 23

■ With the Moon just a half day past exact first quarter (for the Americas), you'll see the terminator between lunar day and night still running almost, but not quite, straight down the Moon's face as shown below.

In a telescope the terminator will cross interesting terrain. In the north (top) it's just beginning to uncover Mare Imbrium, filling the crater pair Aristillus and Autolycus with black shadow on Imbrium's flat floor (left of Mare Serenitatis in the picture below). North and south of them on the terminator are the Alps and Apennines, respectively, some of the Moon's highest mountains. They outline this part of Imbrium's rim.

The southern half of the terminator crosses some of the largest craters of the ancient Southern Highlands. Shadowy Werner and Aliacensis seem to echo the smaller Aristillus and Autolycus pair.

SUNDAY, MAY 24

■ Have you ever seen even one star of Centaurus? Alpha Centauri, famous and bright, never gets above the horizon unless you’re as far south as San Antonio or Orlando (latitude 29° N). But Theta Centauri, shining at a respectable magnitude 2.0, clears your south horizon anywhere in the continental United States and southern Canada. No other star in its area is as bright.

But you have to know where and when to look.

In late May, the time comes about an hour after the very end of twilight. And the place? Theta Centauri (Menkent) is due south almost three fists (27°) lower left of Spica, and just a bit farther (32°) to the right of Antares and a bit lower.

You’ll need an open view low to the south; the farther north you are, the lower. Binoculars will help through light pollution near your south horizon and/or if Theta Cen is so low that atmospheric extinction dims it a lot. Catch it and that’s one more constellation, or at least a piece of one, to add to your life list.

MONDAY, MAY 25

■ The waxing gibbous Moon shines high after dark. Look for Spica about a fist and a half to its left. Denebola, Leo's tailtip, is a little farther to the Moon's upper right.

The three of them form a huge kite-shaped asterism with bright Arcturus, which is much higher to their upper left. The kite is diving down to crash, like so many real kites I knew when I was a kid.

But Arcturus is also the tailpoint of another, more permanent kite. The Kite of Boötes, smaller and much narrower, extends up from Arcturus these evenings, flying stably upright.

TUESDAY, MAY 26

■ The Moon now shines about 5° or 6° to the right of Spica in the south after dark. The two are not companions. The Moon is 1.3 light-seconds away; Spica is about 250 light-years in its background. Nowhere in human experience but astronomy are things so different than they appear.

WEDNESDAY, MAY 27

■ Constellations seem to twist around fast when they pass your zenith — if you're comparing them to your direction "down." Just two weeks ago, the Big Dipper floated horizontally in late twilight an hour after sunset (as seen from latitude 40° N). Now the Dipper is angled diagonally at that time. In just another two weeks it will hang down by its handle.

THURSDAY, MAY 28

■ To most of us, "Cassiopeia" means "Cold." Late fall and winter are when this landmark constellation stands high overhead in the evening (as seen from mid-northern latitudes). But even in the warm evenings of June, it lurks low. As twilight fades out, look for it down near the north horizon: a wide, upright W. The farther north you are the higher it'll appear. But even as far south as San Diego and Atlanta, all of its stars will be above the horizon.

FRIDAY, MAY 29

■ Vega, the Summer Star, is now nicely up in the east-northeast after dark. Look for its faint little constellation Lyra hanging down from it with its bottom canted to the right. Lyra's main pattern consists of a small equilateral triangle with Vega as one upper corner, and a larger parallelogram attached to the triangle's bottom corner.

Binoculars will help through the moonlight. The Lyra pattern is 7½° from end to end, so it will somewhat overspill the field of view in most binoculars.

SATURDAY, MAY 30

■ Full Moon tonight; exactly full at 4:45 a.m. Sunday morning EDT. This a minimoon (sometimes called a "micromoon" but that's way too exaggerated), the opposite of a supermoon. The Moon is just hours from apogee, making this the smallest full Moon of the year. Can you detect the slight difference?

After dusk look for orange Antares 2° or 3° left of it, as shown below. Antares is closer above the Moon by the beginning of dawn. You can reduce the lunar glare by covering the Moon with a finger. Binoculars help even more to reveal the star and its color.

The Moon will occult Antares for eastern Australia and southern South America; details.

SUNDAY, MAY 31

■ With summer three weeks away astronomically speaking, the last star of the Summer Triangle rises above the eastern horizon at the end of twilight. That's Altair, the Triangle's lower-right corner. Its highest and brightest corner is Vega. The third is Deneb, the dimmest of the three, sparkling less far to Vega's lower left.

This Week's Planet Roundup

Mercury emerges into difficult view this week very low in the afterglow of sunset. About 30 or 40 minutes after sundown, look west and follow the line from Jupiter through Venus diagonally down nearly to the horizon. Mercury is bright now, about magnitude –1, but that's before atmospheric extinction.

Every day Mercury will get a little higher in sunset afterglow.

Venus and Jupiter, the two brightest planets, shine in the west during twilight and for about 40 minutes after twilight's end. Venus it the lower and the brighter of the two, at magnitude –3.9. Jupiter is a sixth that bright at magnitude –1.9. Both are in Gemini.

Spot Pollux and Castor upper right of Jupiter. Pollux is slightly the brighter of them.

Watch Venus and Jupiter close in on each other night by night. On Friday May 22nd they're 18° apart. By Friday the 29th they're down to 11° apart. Their conjunction will come on June 9th, when they'll shine 1.6° apart.

Mars and Saturn are low in the east in early dawn. Bring binoculars. Saturn is the higher and brighter of the two at magnitude +0.9. Find it about 10° up almost due east an hour before sunrise. Mars is much lower and somewhat fainter, magnitude +1.3. Look for Mars about two fists to Saturn's lower left, a little farther every morning.

Uranus is in conjunction with the Sun.

Neptune hides low before dawn.

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.

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).

For the necessary tricks, 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 — as it does 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. 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 "plate solving" 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, photography-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 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 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, The Demon-Haunted World: Science as a Candle in the Dark

"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, in the summation of his unpopular, but successful, defense of British soldiers in the Boston Massacre trial

"Truly, whoever can make you believe absurdities can make you commit atrocities."
            — Voltaire, 1765, Questions sur les miracles