The T Cor Bor watch. Every clear evening now, I take a look overhead a third of the way from Arcturus to Vega for Alpha Coronae Borealis, also known as Alphecca. At magnitude 2.2 it's the only moderately bright star in the delicate Northern Crown. Alphecca is easy to see through my light pollution. The rest of Corona Borealis is not.

Keep an eye out a third of the way from Arcturus to Vega. Arcturus shines very high toward the southwest these evenings; Vega is very high toward the east.
Sky & Telescope

Is Alphecca alone? One of these days, it won't be!

The point in Corona Borealis to watch.
Bob King

The recurrent nova T Coronae Borealis, east of Alphecca by 5° (three finger-widths at arm's length) is due for its next eruption following those of 1866 and 1946. Those times it peaked at 2nd or 3rd magnitude, roughly matching Alphecca. T shows uneasy signs of getting ready to erupt again, maybe this summer. See Bob King's Is the Blaze Star About to Blow? You May Be the First to Know with more information, detailed charts, and comparison-star magnitudes so you'll be ready.

Even as it simmers along at its normal 10th magnitude, T CrB is a pretty easy pickup with a small telescope. Give it a look while it's still gathering its forces.

And don't wait for the news to come! T Cor Bor's rise takes just a few hours, and in the past its peak brightness has lasted only about half a day.


■ High in the east the Summer Triangle holds sway after dark. Its top star is Vega, the brightest on the whole eastern side of the sky. The brightest star to Vega's lower left is Deneb. Farther to Vega's lower right is Altair.

With the Moon gone this week you can see the Milky Way (if you're not too light-polluted) running grandly just inside the Summer Triangle's bottom edge. This stretch of the Milky Way includes one of its richest regions, the big Cygnus Star Cloud. Because when we look toward Cygnus, we're looking downstream along the local arm of our galaxy.

■ As evening grows late and even Altair rises high, look left of Altair, by hardly more than a fist, for compact little Delphinus, the Dolphin.

Did you get it? Then try for fainter, smaller Sagitta, the Arrow. It's a little closer to Altair's upper left. The Arrow points toward lower left, past the nose of Delphinus.

■ The last-quarter Moon (exactly last quarter at 5:53 p.m. EDT) rises tonight around 1 a.m. local daylight-saving time. Watch for it to come up below the Great Square of Pegasus. Saturn is about two fists at arm's length to the Moon's upper right. By the time Saturday's dawn begins, you can see that the Moon is not quite halfway between Saturn and Mars.

Mars and Jupiter in early dawn, June 29, 2024
Far lower left of Mars, Jupiter has been getting higher and easier to see, while still low at dawn. Welcome it into its 2024-25 apparition.


■ Right at nightfall, look for the Big Dipper hanging straight down in the northwest. Its bottom two stars, the Pointers, point to the right toward modest Polaris, the end of the Little Dipper's handle, due north.

This is the time of year when, at the end of twilight, the Little Dipper floats straight up from Polaris — maybe like a helium balloon escaped from some evening backyard party. Through light pollution, however, all you may see of the Little Dipper are Polaris at its bottom and Kochab, the lip of the Little Dipper's bowl, at the top. The rest of its stars are fairly dim at 3rd to 5th magnitude.


Mercury and Venus very low to the WNW horizon in bright twilight, June 30, 2024
If you examine the west-northwest horizon in bright twilight day by day, when do you first pick up Mercury? Venus?

■ Dangling lower right from bright Vega high in the east after dark are the main stars of Lyra, forming a small triangle and parallelogram. The two brightest stars of this pattern after Vega are the two forming the bottom of the parallelogram: Beta and Gamma Lyrae, Sheliak and Sulafat. They're currently lined up vertically. Beta is the one on top.

Beta Lyrae is an eclipsing binary. Compare it to Gamma whenever you look up at Lyra. Normally Beta is only a trace dimmer than Gamma. Eventually, however, you'll catch Beta when it is obviously dimmer than usual.

Waning crescent Moon passing Mars and Jupiter, July 1-3, 2024
And now the waning crescent Moon joins those morning planets.


■ Right after nightfall, look due south for orange Antares on the meridian. Around and upper right of Antares are the other, whiter stars forming the distinctive upper-Scorpius pattern. The rest of the Scorpion runs down from Antares toward the horizon, then left.

Three doubles in the top of Scorpius. The "head of Scorpius" is the near-vertical row of three stars upper right of Antares. The top star of the row is Beta (ß) Scorpii or Graffias: a fine double star for telescopes, separation 13 arcseconds, magnitudes 2.8 and 5.0.

Just 1° below Beta is the fainter, very wide naked-eye pair Omega1 and Omega2 Scorpii, tilted to the right of vertical. They're 4th magnitude and ¼° apart. Binoculars show their slight color difference; they're spectral types B9 and G2.

Upper left of Beta by 1.6° is Nu Scorpii, separation 41 arcseconds, magnitudes 3.8 and 6.5. In fact this is a telescopic triple. High power in good seeing reveals Nu's brighter component itself to be a close binary, separation 2 arcseconds, magnitudes 4.0 and 5.3, aligned almost north-south.


■ The two brightest stars of summer, Arcturus and Vega, are about equally high overhead right after dark: Arcturus toward the southwest, Vega toward the east. Arcturus used to be the higher one. Now Vega stakes claim to that status for the rest of the year.

■ At dawn Wednesday morning, Jupiter and the thin waning crescent Moon hang 4° or 5° apart low in the east-northeast, as shown above. Find Mars about 20° (two fists) to their upper right. Don't wait too long or the sky will get too bright!


■ To casual starwatchers or those with an obstructed northern view, Cassiopeia in July might sound as wrong as Christmas in July. But already Cas has passed its lowest evening position of the year and is gradually gaining altitude in preparation for the coming fall and winter. Look for its W shape low in the north-northeast after dark. The W is still almost level.


■ The Big Dipper, high in the northwest, starts turning around as the night advances to "scoop up water" through the evenings of summer and early fall.


■ The largest asteroid, 1 Ceres, is at opposition in the handle of the Sagittarius Teapot. It's in binocular range at magnitude 7.3. Use the finder chart in the July Sky & Telescope, page 48. The ticks on its track there mark its position at 0:00 UT on the dates indicated, which for the Americas falls on the afternoon or evening of the previous date.

From now through July 12th Ceres is less than 1° from the bottom star of the Teapot's handle. On the night of July 14th, it will be 0.6° north of the little 8th-magnitude globular cluster M54.

■ Earth is at aphelion today, its farthest from the Sun for the year, just 3.3% farther than at perihelion in January.

■ New Moon, exactly so at 6:57 p.m. EDT (22:57 UT).


■ This evening about 20 or 30 minutes after sunset, try to sight the extremely thin young crescent Moon low in the west-northwest. Will this be your record youngest Moon? For most of North America, you're seeing it only 25 to 28 hours old depending on where you are. Compare the time of your sighting with the time of new Moon under Friday above.

Thin waxing crescent Moon with very low Mercury and Venus after sunset, July 6-7, 2024.
After ending one lunation and starting another, the Moon returns as an extremely thin waxing crescent very low after sunset to accompany Mercury. And maybe Venus; use binoculars.


■ The two-day-old crescent Moon points the way down to Mercury in bright twilight, as shown above. Try for Venus too, way down farther to Mercury's lower right. Good luck.

This Week's Planet Roundup

Mercury is very low in the west-northwest during bright evening twilight. It fades this week from magnitude –0.7 to –0.2.

Venus is very deep in evening twilight farther to Mercury's lower right. Their separation widens from 9° on June 28th to 13° on July 4th. Try for Venus with binoculars about 15 minutes after sunset. At least Venus is bright, magnitude –3.9.

Both Mercury and Venus will get a bit higher in the next couple of weeks.

Mars (magnitude 1.0, in Aries) is fairly well up in the eastern sky just before and during early dawn. It's about two fists upper right of brighter Jupiter, much lower.

Jupiter (magnitude –2.0, in Taurus) lurks very low in the east-northeast in early dawn.

Saturn (magnitude 1.1, near the Aquarius-Pisces border) rises around midnight and shines well up in the southeast before dawn. Find the Great Square of Pegasus two fists upper left of it, and Fomalhaut sparkling two fists to Saturn's lower right.

Saturn with rings nearly edge-on, June 1, 2024
Saturn's rings this season are nearly edge-on. Note the stark black shadow they cast southward, that is toward the top of the image. Christopher Go, in the low-latitude Philippines, took this image shortly before sunrise on June 1st.

Uranus, magnitude 5.8, is between Jupiter and Mars. But that's still too low in the dawn for something so faint.

Neptune, magnitude 7.9 in Pisces, is about 10° lower left of Saturn before dawn begins if you have large binoculars or a telescope, a detailed enough finder chart showing Neptune's current location among the similar-looking faint stars around it, and skill in using sky charts with binocs or a scope.

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.

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), which shows all stars to magnitude 7.6.

Pocket Sky Atlas cover, Jumbo edition
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 outdoors 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. (It's currently out of print.) The next up are the even larger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to mag 9.75). 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 top of the hill for total astro-geeks is the Annals of the Deep Sky series, currently at 10 volumes as it slowly works forward through the constellations alphabetically. So far it's only up to F.

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 the sky. And 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 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. 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."
             John Adams, 1770


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