Special to CosmicTribune.com, July 29, 2024

Excerpts from weekly Sky&Telescope report.

SATURDAY, JULY 27

■ Last-quarter Moon (exact at 10:52 p.m. EDT). The Moon, in Pisces, rises around 11 or midnight tonight below the head of Andromeda and the Great Square of Pegasus.

SUNDAY, JULY 28

■ Starry Scorpius is sometimes called “the Orion of Summer” — for its brightness, its blue-white giant stars, and its prominent red supergiant (Antares in the case of Scorpius, Betelgeuse for Orion). But Scorpius passes a lot lower across the southern sky than Orion does, for those of us at mid-northern latitudes. That means it has only one really good evening month: July.

■ The rich tail-of-Scorpius area is at its best low in the south right after complete nightfall, as shown below. Find it lower right of the Teapot’s spout by a fist at arm’s length or less. Or, about a fist and a half lower left of Antares.

Shaula and Lesath in the tail of Scorpius are the “Cat’s Eyes.” Halfway between them and the spout of the Sagittarius Teapot is the big bright open cluster M7. Nearly 4° upper right of M7 is smaller, dimmer M6. And the Cat’s Eyes point west (right) to Mu Scorpii, a much closer pair known as the Little Cat’s Eyes. Stellarium

Spot the two stars especially close together in the tail. These are Shaula and Lesath, Lambda and Upsilon Scorpii, also known as the Cat’s Eyes. They’re unequal and canted at an angle; the cat has a bleary eye and is tilting his head to the right. They’re magnitudes 1.6 and 2.6. Both are blue-white supergiants, 700 and 500 light years away, respectively. Yes, the fainter one, Lesath, is the nearer one.

Between the Cat’s Eyes and the Teapot’s spout are the open star clusters M7 and M6, showy speckle-splashes in binoculars. M7 is the bigger and brighter one; M6 is more subdued.

MONDAY, JULY 29

Standing atop Scorpius, and butting heads with Hercules much higher, is enormous Ophiuchus the Serpent-Holder. Just east of his east shoulder (Beta Ophiuchi) is a dim V-shaped asterism like a smaller, fainter Hyades. This is the defunct constellation Taurus Poniatovii, “Poniatowski’s Bull.” The V is 2½° tall and stands almost vertically now.

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

Just 1¼° NNE of Beta Oph is the large, loose open cluster IC 4665, a nice binocular object.

TUESDAY, JULY 30

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

WEDNESDAY, JULY 31

■ Look low in the northwest or north at the end of these long summer twilights. Would you recognize noctilucent clouds if you saw them there? They’re the most astronomical of all cloud types, what with their extreme altitude and, sometimes, their formation on meteoric dust particles. They used to be rare, but they’ve become more common in recent years as the atmosphere changes.

THURSDAY, 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. During the many centuries after this tradition took hold in Europe and the British Isles, the calendar drifted with respect to Earth’s position in its orbit (until our Gregorian calendar was instituted a few centuries ago to halt such problems). So in 2024, the midpoint between the June solstice and the September equinox actually falls on August 6th, at 12:47 p.m. Eastern Daylight Time (16:47 UT).

FRIDAY, AUGUST 2

■ Week by week, Venus is getting just a little less low in the sunset. Using optical aid, can you pick it up and then detect Regulus and Mercury to its left, as indicated below?

Venus, Regulus, and Mercury have reconfigured themselves, if you can detect them so low through bright twilight.

SUNDAY, AUGUST 3

■ Bright Vega passes closest to overhead around 10 or 11 p.m., depending on how far east or west you live in your time zone.

How closely Vega 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 exactly straight up you need to be farther north, at latitude 45°: Portland, Minneapolis, Montreal, southern Maine, southern France, northern Italy, Odesa, Kherson.

  July 28-Aug. 3: Open clusters M6 and M7 in the South, The Sky