This Week's Sky at a Glance, July 24 – August 2

FRIDAY, JULY 24

■ The gibbous Moon tonight shines near Antares, an orange-red supergiant — "the Betelgeuse of summer" — as shown below.

■ Fourth star of the Summer Triangle. The brightest star that's fairly near the Summer Triangle is Rasalhague (Alpha Ophiuchi), the head of Ophiuchus. Use it to turn the Summer Triangle into a giant diamond gem. Look very high toward the southeast after dark, and the scene will be like this:

SATURDAY, JULY 25

■ Now the Moon after dark shines over the tail of Scorpius, as shown at the top of this page. Closer to the left of it is the spout of the Sagittarius Teapot.

■ As summer progresses, bright Arcturus moves down the western side of the evening sky. Its pale ginger-ale tint always helps identify it.

Arcturus forms the bottom point of the Kite of Boötes. The Kite, rather narrow, extends upper right from Arcturus by 23°, about two fists at arm's length. The lower right side of the kite is dented inward, as if some invisible celestial intruder once had a fender-bender with it.

SUNDAY, JULY 26

■ Now the thickening Moon shines in the top of the Sagittarius Teapot. Cover the Moon with your finger to reduce its star-hiding glare in your eyes.

■ More Arcturus. Look again to Arcturus high in the west. In astronomy lore today, Arcturus may be best known for its cosmic history: It's an orange giant some 7 billion years old, older than the solar system, racing by our part of space on a trajectory that indicates it was born in another galaxy: probably one of the many dwarf galaxies that have fallen into the Milky Way and merged with it over the ages.

But in the astronomy books of our grandparents, Arcturus had a different claim to fame: It turned on the lights of the 1933 World's Fair in Chicago, launching the nation's celebration of "a century of progress." Astronomers rigged the newly invented photocell to the eye end of observatory telescopes around the US and aimed them where Arcturus would pass at the appointed moment on opening night. Where the sky was clear the star's light crept onto the cells, the weak signals were amplified and sent over telegraph wires to Chicago, and on blazed the massive lights to the cheers of tens of thousands.

Why Arcturus? Astronomers at the time thought it was 40 light-years away (modern value: 36.7 ±0.2). So the light would have been in flight since the previous such great event in Chicago, the World's Columbian Exhibition in 1893.

And earlier? Arcturus was famous as one of the first stars discovered to show proper motion, its own independent motion on the celestial sphere. In 1718 Edmond Halley found that Arcturus, Sirius, and Aldebaran had moved more than half a degree from where the Greek astronomer Hipparchus measured them to be some 1,850 years earlier.

And before that? Arcturus was the first nighttime star that anyone saw in the daytime with a telescope: by Jean-Baptiste Morin in 1635.

MONDAY, JULY 27

■ The Moon this evening shines by the handle of the Teapot. The Moon now forms a big, flattish isosceles triangle with Altair 3½ fists to its upper left and Antares the same distance to its right.

TUESDAY, JULY 28

■ Full Moon this evening and tomorrow evening. The Moon is exactly full at 10:36 a.m. EDT on the morning of the 29th, which is about halfway between Tuesday and Wednesday evenings for the Americas.

Once the Moon is well up, you'll find that it's between the Sagittarius Teapot to its right and the dim boat-shape pattern of Capricornus closer to its left.

WEDNESDAY, JULY 29

■ We're not yet halfway through summer, but already W-shaped Cassiopeia, a constellation of fall and winter evenings, is climbing up in the north-northeast as evening grows late. And the Great Square of Pegasus, emblem of fall, comes up to balance on one corner over the eastern horizon.

THURSDAY, JULY 30

■ More Cassiopeia: Notice that the upper side of the W is the brightest side. This is always true when Cas is climbing in the northeast. The brighter side is the lower one whenever Cas is declining in the northwest.

■ Watch Cas rise higher and straighten more upright through the next two hours and, equivalently, through the next month. The rule to always remember for the turning of the sky: two hours later is the same as one month later.

Why so?

Because the direction into space you look when you're face into your night sky depends on two things: Earth's 24-hour rotation, and which way Earth's night side — the side away from the Sun — faces in space during Earth's 12-month orbit around the Sun. So, looking 2 hours later in the night turns your view as much as looking 1 month later in the year.

FRIDAY, JULY 31

■ Bright Vega passes its closest to straight overhead around 11 p.m., depending on how far east or west you live in your time zone.

How closely it misses your zenith depends on how far north or south you are. It passes right through your zenith if you're at latitude 39° north (Washington DC, Cincinnati, Kansas City, Lake Tahoe). How closely can you judge this just by looking?

Deneb crosses closest to the zenith almost exactly two hours after Vega. But to see Deneb straight up you need to be farther north, close to latitude 45°: Portland, Minneapolis, Montreal, central Maine, southern France, northern Italy, Odesa, Kherson.

SATURDAY, AUGUST 1

■ Today is Lammas Day or Lughnasadh, one of the four traditional "cross-quarter" days midway between the solstices and the equinoxes. Sort of. In the many centuries after this tradition took hold in Europe and the British Isles, the calendar drifted with respect to Earth's position in orbit (until our Gregorian calendar was instituted a few centuries ago to deal with such problems). So in 2026, the midpoint between the June solstice and the September equinox actually falls on the night of August 6- 7, at 12:13 a.m. Eastern Daylight Time (9:13 p.m. Pacific Daylight Time).

That minute is the exact center-balance of astronomical summer: the very top of the circle of the year as defined by the astronomical seasons (for the Northern Hemisphere; the bottom of the year for the Southern Hemisphere.)

SUNDAY, AUGUST 2

■ Standing atop Scorpius in the south-southwest after dark, and butting heads with Hercules much higher, is enormous Ophiuchus the Serpent-Holder. East of his east shoulder (Beta Ophiuchi, Cebalrai) is a dim V-shaped asterism like a smaller, fainter Hyades. This is the face of the defunct constellation Taurus Poniatovii, "Poniatowski's Bull." The V is 2½° tall. It stands almost vertically right after nightfall now. ¹

The top two stars of the V are the faintest (magnitudes 4.8 and 5.5). The middle star of its left (east) side is the famous K-dwarf binary 70 Ophiuchi, visual magnitudes 4.2 and 6.2, distance just 17 light-years (the same as Altair). The two stars of the pair are currently 6.7 arcseconds apart in their 88-year orbit: close but nicely separated at medium-high power in any telescope.

Just 1¼° NNE of Beta Oph (Cebalrai) is the large, very loose open cluster IC 4665, a binocular target 1,100 light-years away. That's relatively near for an open cluster, which accounts for its rather large apparent size; it's a little more than ½° across.

If you orient your view so celestial SSW is up — in other words putting Beta Oph straight above the group — its central stars spell out a ragged but more-or-less legible welcome: "HI".

The "HI" will be in mirror writing if your view is mirror-reversed. That happens whenever your optical system has an odd number of reflections, such as if you use a star diagonal at the eyepiece.

For more telescopic sights in this area, including Barnard's Star, doubles in IC 4665, and two other clusters, see Ken Hewitt-White's "Suburban Stargazer" section in the July 2025 Sky & Telescope, page 55. (The text there misidentifies Collinder 350 as "359".)

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This Week's Planet Roundup

Mercury is visible low in the dawn this week. Look for it low above the east-northeast horizon about 40 or 50 minutes before sunrise. It'll be faint as Mercury goes, but it's brightening daily: from magnitude +1.7 on Saturday morning the 25th to +0.3 on Saturday morning August 1st. (Don't confuse it with fainter Pollux and Castor about a fist to its left and upper left.)

Venus continues to shine brightly (magnitude –4.3) as the "Evening Star" low in the west in twilight. It still sets around twilight's end.

In a telescope, Venus is a brilliant, very slightly gibbous disk (58% sunlit) 20 arcseconds from pole to pole. Catch it as soon in late afternoon or early dusk as you can, before it sinks low into poorer atmospheric seeing.

Venus will remain in twilight view until the end of the summer, gradually lower, enlarging while waning in phase.

Mars (magnitude +1.3, in Taurus) glows in the east in early dawn. Aldebaran, its near-twin for brightness and color, twinkles to its right or upper right. The horntip stars of Taurus, fainter, shine closer to Mars's left.

Mars is still on the far side of its orbit from us. So in a telescope it's only a tiny, fuzzy blob 4½° arcseconds wide.

Jupiter is hidden in conjunction with the Sun.

Saturn (magnitude +0.6, at the Pisces-Cetus border) rises in the east around 11 or midnight. Once it's up find it below the Great Square of Pegasus, which is balanced on one corner.

Saturn is best placed for telescopic viewing high in the southeast before the first light of dawn. It's the brightest thing in its dim area. (Don't confuse it with Fomalhaut, its near-twin in brightness, twinkling a good four fists to Saturn's lower right.)

Late last fall Saturn's rings turned nearly edged-on to Earth and almost disappeared. Now the rings' inclination has widened back up to 14°.

Uranus (magnitude 5.8, in Taurus) hides in the background about 15° west of Mars along the ecliptic.

Neptune (magnitude 7.9, at the Pisces/Cetus border) hides even farther in the background 10° west of Saturn. You'll need detailed finder charts to tell Uranus and Neptune from stars of similar brightness.

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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 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.

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 units, relatively low priced. 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).

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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, 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

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1. Taurus Poniatovii was invented by the rector of Vilnius University, Marcin Poczobut, in 1773 to flatter his ruler Stanislaus Poniatowski, the King of Poland and Grand Duke of Lithuania. The Poniatowski family coat of arms displayed a bull. Poczobut may have needed money for the university; scholars in those days often had to obsequiously, embarrassingly, flatter up their monarchs and oligarchs for funding.² Recently, some echoes of this old requirement have returned in the United States.

The V asterism in Poniatowski's Bull was meant to echo the real Taurus's face formed by Aldebaran and the brightest Hyades. The rest of the little bull trailed off to the northeast. A few star mappers included it on their sky charts for a while, since Poczobut was respected as an astronomer; J.-J. de Lalande used some of his fine positional measurements to help calculate the orbit of Mercury. But the bull on his king's coat of arms has long since dropped from the sky.

Nevertheless, today "a depiction of the constellation can be found on the wall of the Vilnius University Astronomical Observatory" per Wikipedia. I can't find a photo of that online. Today Vilnius University thrives in a free Lithuania. Can somebody there go look through the observatory? If you find Taurus Poniatovii on the wall where it was born, please send me pics: [email protected].

2. For instance, see the elaborate title pages by Galileo fawning over the Medicis and by Kepler buttering up his "Roman" Emperor Rudolph II.  William Herschel, originally from what is now Germany, named his new planet (now Uranus) "The Georgian Star" to magnify his financial patron, England's King George III. Herschel's 1781 letter to the Royal Society announcing this name (and using the long s ) drips with flattery:

"Georgium Sidus" went over very badly outside England. French astronomers called the planet Herschel, following the lead of Charles Messier. Others proposed Astraea, Cybele, Minerva, and more names. After bitter international debates, astronomers beyond England eventually settled on Uranus — a variant on the Greek deity considered the father of Saturn, just as Saturn was the father of Jupiter. But the English shunned the name Uranus for nearly 70 more years.

All well and good. But "Uranus" was actually proposed by the German astronomer Johann Elert Bode only four months after Herschel named the planet for his funder. I've wondered if Bode may have had a covert second purpose for the name (its last four letters mean the same in Latin and English) as a low joke for "you're [a] kiss-ass": a term for "obnoxious sycophant" that was already in use at the time in both English and German.

I've never seen a trace of evidence for this notion, other than the name being the butt of jokes for well over a century. (Albert Stern has attempted to find the first recorded Uranus joke. The earliest clear one he found is from 1881, and he turned up possibles from the 1870s and 1852. And he was only looking in U.S. publications.) Elsewhere we read that "Exactly why Bode proposed the Latinized name Uranus over the Greek name for the god of the sky (Ouranus) is unclear. Also, it’s unclear why Bode did not use the Roman name for the god, Caelus, in keeping the with the Roman names of the other planets," including Saturn and Jupiter.

Could Bode have been subtly satirizing his emigré former countryman for sucking up so blatantly to the English king?

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