The Southern Delta Aquariid meteor shower continues to ramp up this week. The shower won’t peak until the end of July, but you should see some of its meteors in the hours before dawn. The best time to look is between 3 and 4 a.m. local daylight time, just before twilight begins. Viewing conditions will be great this week because the Moon will be gone from the predawn sky. Unfortunately, our satellite will show a fat gibbous phase at the shower’s peak the night of July 29/30. To tell a Southern Delta Aquariid meteor from a random dust particle burning up in Earth’s atmosphere, trace the streak of light’s path backward. A shower meteor will appear to originate from the constellation Aquarius the Water-bearer.
The Moon reaches perigee, the closest point in its orbit around Earth, at 4:25 a.m. EDT. It then lies 222,097 miles (357,431 kilometers) away from us. Since perigee arrives less than six hours after yesterday evening’s New Moon, residents of coastal areas can expect to see tides rise higher than normal for the next couple of days.
Saturday, July 14
Look for a slender crescent Moon 2° above Mercury in this evening’s sky. A half-hour after the Sun goes down, the Moon hangs 9° (the approximate width of your closed fist when held at arm’s length) above the western horizon. Through binoculars, both objects should stand out against the colorful twilight background. A telescope reveals the magnitude 0.5 planet’s disk, which spans 8″ and shows a crescent phase.
Sunday, July 15
The Moon moves approximately 13° eastward relative to the starry background every 24 hours, and that motion carries it near Venus this evening. The crescent Moon appears just 2° to the right of the brilliant planet, which gleams at magnitude –4.2. The stunning duo stands 15° high in the west 45 minutes after sunset. This conjunction provides a nice photo opportunity. If you shoot the twilight scene before 9:30 p.m. local daylight time, you’ll also capture Regulus to the lower right and Mercury even closer to the horizon. When viewed through a telescope, Venus appears 18″ across and nearly two-thirds lit.
Monday, July 16
Observers with telescopes should get their first good views of Comet 21P/Giacobini-Zinner before dawn in mid-July. The comet currently glows at 10th magnitude against the photogenic northern Milky Way of southern Cepheus. This morning, Giacobini-Zinner lies midway between 3rd-magnitude Zeta (ζ) Cephei and 4th-magnitude Delta (δ) Cep.
Mars remains a stunning sight all week. It rises around 9:30 p.m. local daylight time this evening and climbs nearly 30° high in the south by 2 a.m. It currently shines at magnitude –2.6 — brighter than every other nighttime celestial object except for the Moon and Venus — and sports a 23.6″-diameter disk when viewed through a telescope. Don’t expect to see much detail on the disk, however — the Red Planet is currently in the throes of a global dust storm. The Red Planet will reach opposition in just 10 days, when it will appear 0.2 magnitude brighter and nearly 1″ bigger.
Wednesday, July 18
This week offers a good opportunity for binocular users to track down one of summer’s finest open star clusters. NGC 6231 lies in the tail of Scorpius the Scorpion, just 0.5° north of the double star Zeta (ζ) Scorpii (which is another fine binocular sight). NGC 6231 shines at magnitude 2.6 and packs more than 100 stars into a region just 14′ in diameter. This part of Scorpius lies nearly due south after darkness falls, though it doesn’t climb high from mid-northern latitudes.
Thursday, July 19
First Quarter Moon occurs at 3:52 p.m. EDT. By the time the Sun sets this evening for North American observers, the Moon appears in the south-southwest and nearly halfway from the horizon to the zenith. As darkness descends, our satellite grows more prominent and the background stars of Virgo the Maiden come into view. Look for 1st-magnitude Spica to the Moon’s lower right and brilliant Jupiter to its left
Friday, July 20
The Moon’s eastward motion carries it near magnitude –2.2 Jupiter tonight. Our satellite, which now sports a noticeable gibbous phase, stands 4° above the planet as twilight fades to darkness. If you point a telescope at Jupiter, you’ll see spectacular cloud-top detail on a flattened disk that spans 39″ across the equator. You’ll also see the gas giant’s four biggest and brightest moons.
Perhaps no month better epitomizes summer in the Northern Hemisphere than July. And this month finds the season’s namesake asterism, the Summer Triangle, on prominent display. The trio’s brightest member, Vega in the constellation Lyra the Harp, stands nearly overhead shortly before midnight. The asterism’s second-brightest star, Altair in Aquila the Eagle, then lies more than halfway from the southeastern horizon to the zenith. Deneb, the luminary of Cygnus the Swan, marks the Summer Triangle’s third corner. Although it is this asterism’s dimmest star, it’s the brightest point of light in the entire northeastern sky.
Sunday, July 22
Magnificent Saturn reached its peak less than a month ago, when it appeared opposite the Sun in the sky, and our view of the ringed planet remains spectacular. It is on display nearly all night among the background stars of northern Sagittarius, hanging in the south-southeast as darkness falls and climbing highest in the south around 11 p.m. local daylight time. Saturn continues to shine brightly, too, at magnitude 0.1. When viewed through binoculars, you’ll find the Trifid Nebula (M20) 3.2° to the west, with the even brighter Lagoon Nebula (M8) 1° south of the Trifid. Open cluster M25 resides 5.0° northeast of the planet and globular cluster M22 is 4.8° east-southeast of the ringed world. But the best views of Saturn come through a telescope, which reveals the planet’s 18″-diameter disk surrounded by a dramatic ring system that spans 41″ and tilts 26° to our line of sight.