Special to CosmicTribune.com, June 16, 2025

Excerpts from weekly Sky&Telescope report.

MONDAY, JUNE 16

■ Mars and Regulus shine closest together in the west this evening, as shown below. Tonight they’re 0.8° apart (for the Americas), about the width of a pencil held at arm’s length. This is a great time to compare their contrasting colors in binoculars or a telescope at low power.

On paper, Mars is now essentially identical in brightness to Regulus: they’re magnitudes 1.4 and 1.34, respectively. But several factors complicate things, as happens everywhere in nature. Mars’s dark surface markings make one side of the planet a trace darker than the other. Unusual amounts of dust in the Martian atmosphere brighten the globe.

TUESDAY, JUNE 17

■ Mars and Regulus are again 0.8° apart during evening for the Americas, this time with Mars more directly above the star.

WEDNESDAY, JUNE 18

■ Last-quarter Moon (exact at 3:19 p.m. EDT on this date). Look east just as dawn begins tomorrow morning the 19th, about two hours before sunrise, for Saturn glowing 4° or 5° to the Moon’s right (for North America). By then the Moon will be about half a day past last quarter and its terminator will be starting to look a bit concave. The terminator always appears to move fastest across the Moon’s apparent face at first and last quarter.

Upper left of the Moon and Saturn will be the Great Square of Pegasus, a very early harbinger of fall for early risers even before summer begins.

THURSDAY, JUNE 19

■ Comparing Hercules globular clusters. M13 in the edge of the Keystone of Hercules is famous as one of the best and brightest globular star clusters in the sky. It’s now high in the east after dark. But part of its fame is due to its easily findable location. Less known is its near-twin of a “great cluster in Hercules,” M92 in sparser wilderness 9½° to the northeast, as shown below. M92 is only slightly smaller that M13 and has a look of its own.

“To really appreciate the personalities of these two Hercules clusters, try rapidly going back and forth between them,” writes Matt Wedel in his Binocular Highlight column in the June Sky & Telescope. “Most of the visible differences are down to physical size, with M13 being almost twice as massive as M92. Regardless, each is worthy of the title ‘showpiece object.’ ”

Most deep-sky objects look a lot smaller and fainter than you might think. The great globular star clusters M13 and M92, so dramatic in closeup images as cities of thousands of stars, show their true sizes with respect to constellation parts in this image spanning 35°. You can see why you need to get good at star-hopping from map to sky in order to find faint fuzzies with a telescope.Celestial east is roughly down and celestial north is roughly to the left; this is the scene as you see it when looking high into the eastern sky on late-spring evenings.
Starry Night Pro

FRIDAY, JUNE 20

■ It’s the longest day and the shortest night of the year for the Northern Hemisphere. Summer begins at the solstice, 10:42 p.m. EDT on this date; 7:42 p.m. PDT; 2:42 June 21st Universal Time.

This is also when (in the north temperate latitudes) the midday Sun passes the closest it ever can to being straight overhead, and thus when your shadow becomes the shortest it can ever be where you live. This happens at your local apparent [i.e. solar] noon, which is probably rather far removed from noon in your civil (clock) time.

And if you have a good west-northwest horizon (in mid-northern latitudes), mark carefully where the Sun sets as seen from a particular spot. In a few days you should be able to detect that the Sun is again starting to set a just little south (left) of that point, as it begins its six-month journey to the winter solstice.

■ Tonight and in the coming weeks, watch Mars and Regulus draw farther apart as they sink in the west during and after late twilight. Tonight they’re 2° apart as shown below. In a week they’ll be 6° apart and somewhat lower.

Now Mars is pulling away from Regulus in its movement against the stars. From an Earthbound skywatcher’s point of view, Regulus slides toward the lower right with respect your western horizon while Mars does so more slowly.

SATURDAY, JUNE 21

■ Look east-northeast at least an hour before Sunday’s sunrise for the waning crescent Moon passing Venus, as shown below. This is a rather distant Moon-Venus passage; they’ll never be less than 6° apart.

The waning Moon passes widely north of the “Morning Star Venus in the next few mornings

SUNDAY, JUNE 22

■ After dark, look southeast for orange Antares, “the Betelgeuse of summer.” (Both are 1st-magnitude “red” supergiants). Around and upper right of Antares are the other, whiter stars of upper Scorpius, forming their familiar, distinctive pattern. The rest of the Scorpion runs down from Antares, then left. The farther north you are, the lower Scorpius will appear.

Also right after dark, spot Arcturus way up high toward the southwest. Three fists below it is Spica.

  June 16-22: Shortest night on June 20, The Sky