A Guide to the Summer Constellations — Nights When the Milky Way Flows
From the Summer Triangle overhead to Scorpius and Sagittarius on the southern horizon, summer is the season when the Milky Way streams across the sky. Here is your journey through the summer sky — finding the stars of the Herdsman and the Weaver Girl and gazing into the heart of our galaxy.
Overhead — the Summer Triangle
The starting point for summer observing is three stars shining near the top of the sky. Around 10 p.m. from July to August, Vega in Lyra, Deneb in Cygnus, and Altair in Aquila rise high overhead, forming a large triangle. This "Summer Triangle" shows clearly even in the city, making a dependable reference for finding the summer constellations.
The brightest, whitest star is Vega; the one a little to its southeast is Altair. The Milky Way crosses like a river between the two, and in East Asia this band of light is the "Silver River" that separates the Herdsman and the Weaver Girl — the tale of the two meeting on a bridge of magpies on the seventh night of the seventh lunar month was born from these very stars.
A cross and a swan — star-hopping through Cygnus
Begin at Deneb, one vertex of the triangle. Deneb marks the tail of Cygnus the Swan; follow the Milky Way southwest from here and the stars of the body stretch out in a long line, ending at the beak star Albireo. The shape of outstretched wings and a long body is so distinct that it is also called the "Northern Cross." Cygnus flies right through the middle of the Milky Way, so under a dark sky the blend of stars and star-clouds makes it the crowning sight of the summer sky.
Albireo at the tip of the beak, seen through a small telescope, is a lovely double star of one golden and one blue component side by side — a perennial favorite of summer-night telescope viewing. And right beside Vega in Lyra hides the "Ring Nebula (M57)," a doughnut with a hole through the middle, well worth seeking out with a small telescope.
Low in the south — Scorpius, Sagittarius, and the galactic center
Close to the southern horizon lies another star of the summer sky. Scorpius sprawls in a great S-shaped fishhook with the red heart of Antares at its center — a star that blazes red, true to its name meaning "rival of Mars." To its left (east), Sagittarius is easy to find, its six bright stars forming the shape of a "Teapot."
The direction the Teapot's spout points is the center of our galaxy. Under a dark sky away from the city, the Milky Way here swells at its densest and most spectacular, hiding nebulae like the "Lagoon Nebula (M8)" and "Trifid Nebula (M20)" and countless star clusters — enough to sweep through all night with binoculars alone. Because Scorpius and Sagittarius pass low across the southern sky, the more open your southern horizon, the better.
The summer Milky Way and its nebulae and clusters
Summer is the best season of the year for seeing the Milky Way. We look toward the center of our own galaxy, so a river of light crosses the sky from Sagittarius, through Cygnus, all the way to Cassiopeia. Under a truly dark country sky, even the dark rifts within the Milky Way (dark nebulae) come into view, and you feel firsthand why people of old called it the "River of the Sky."
With a single pair of binoculars, the summer Milky Way becomes a treasure chest. The "Eagle Nebula (M16)" and "Omega Nebula (M17)" above Sagittarius, the dense star-cloud "M11 (the Wild Duck Cluster)" in Scutum, the open clusters throughout Cygnus — just sweeping slowly along the Milky Way brings out endless hazy nebulae and clusters studded with stars. In mid-August the Perseid meteor shower reaches its peak, making it a fine time to watch for meteors while you take in the Milky Way.
Best times and directions to observe
The summer constellations are best observed between 9 and 11 p.m. from July through August. By then the Summer Triangle has climbed high overhead and Scorpius and Sagittarius hang due south, letting you take in the whole Milky Way at once. A mountain, seashore, or lakeside open all the way to the southern horizon is ideal.
The biggest variables for summer-night observing are humidity and monsoon-season clouds. Aim for late July to August after the rainy season lifts, and for clear, dry nights around the new Moon. It is a season of mosquitoes, so bring long sleeves and repellent, and to spare your neck, lie back on a mat and gaze up at the Milky Way for the most relaxed way to enjoy a summer night.