Seasonal Observing
Summer Amateur Astronomy
Summer is the most rewarding season for amateur astronomers in the Pacific Northwest — despite the shorter nights. From July through September, the core of the Milky Way arches overhead, bringing with it the greatest concentration of deep-sky showpieces visible from our latitude. Globular clusters, emission nebulae, open clusters, and the dense star clouds of Sagittarius all reach their best positions in the evening sky.
Yes, nights are short — astronomical darkness doesn't arrive until around 11 PM in July from Corvallis. But the skies are reliably clear in a way that winter and spring rarely match. Head out to Adair County Park on a new-moon weekend and you'll find some of the best observing of the year.
The Summer Triangle
Three brilliant stars form the unmistakable Summer Triangle, the dominant asterism of the summer sky:
| Star | Constellation | Magnitude | Distance |
|---|---|---|---|
| Vega | Lyra | 0.0 | 25 light-years |
| Deneb | Cygnus | 1.3 | ~2,600 light-years |
| Altair | Aquila | 0.8 | 17 light-years |
Vega — the brightest of the three — passes nearly overhead from Corvallis in summer. It is a blue-white A-type star that served as the north celestial pole about 12,000 years ago and will again in another 12,000 years due to Earth's precession.
Deneb is the most remarkable. At roughly 2,600 light-years away it appears similar in brightness to nearby Vega — meaning it is intrinsically one of the most luminous stars in our galaxy, perhaps 200,000 times the Sun's luminosity. If it were as close as Vega, it would cast shadows at night.
Best Summer Deep-Sky Objects
Sagittarius and the Galactic Core
Low in the south from Oregon, Sagittarius holds an extraordinary concentration of deep-sky objects because we are looking directly toward the center of the Milky Way, roughly 26,000 light-years away. On a dark night the Sagittarius Star Cloud (M24) appears as a detached bright patch of the Milky Way — a window through gaps in the dust clouds revealing billions of stars beyond.
Large emission nebula with embedded star cluster. Visible to the naked eye from dark sites as a hazy patch. Pink glow in long-exposure photos.
Three-lobed emission nebula divided by dark dust lanes — stunning in photographs. Requires dark skies and moderate aperture visually.
One of the finest globulars in the sky and one of the closest at ~10,000 light-years. Rivals M13 in Hercules when high enough in the south.
Not a single object but a window through the dust. Best viewed with binoculars or a rich-field telescope at low power.
Scorpius
Scorpius, the Scorpion, skims low along the southern horizon from Oregon — its tail barely clears the horizon — but it rewards those who catch it on clear summer nights. The heart of the scorpion is Antares, a red supergiant so large that if placed at the Sun's position it would engulf Mars. Binoculars reveal its subtle orange-red color against the rich star fields behind it.
Several fine globular clusters reside in Scorpius: M4 is one of the closest globulars to Earth (~7,200 light-years) and is large and loose enough that moderate aperture resolves individual stars across its face. M80 is smaller but more concentrated and dramatic.
Hercules Globular — M13
The showpiece globular cluster of the northern sky, M13 in Hercules is high overhead on summer evenings and accessible in binoculars as a fuzzy star. In a 6-inch or larger telescope it resolves into countless stars — an estimated 300,000 suns packed into a sphere about 150 light-years across, located 25,000 light-years away.
The Ring Nebula — M57
In the small constellation Lyra, between the two southern stars of the parallelogram near Vega, sits M57 — the Ring Nebula. A planetary nebula (the glowing shell expelled by a dying Sun-like star), it appears as a tiny smoke ring even in modest telescopes. At high magnification the ring structure is unmistakable. The white dwarf remnant at its center is 15th magnitude and requires large aperture to see.
The Dumbbell Nebula — M27
The Dumbbell Nebula in Vulpecula is the largest and brightest planetary nebula in the sky. Unlike M57's thin ring, M27 presents a full apple-core or bow-tie shape. It is easily found by star-hopping from the tip of Sagitta (the Arrow) and is a satisfying object in any telescope.
The Perseid Meteor Shower
Every August, Earth passes through the debris trail of Comet Swift-Tuttle, producing the Perseid meteor shower — the most popular and reliable meteor shower of the year. Peak rates of 50–100 meteors per hour under dark skies occur around August 11–13, with the radiant in Perseus rising in the northeast after midnight.
No equipment needed — just a reclining chair, a sleeping bag, and dark skies. The Perseids are fast meteors that frequently leave persistent glowing trains. Watch for the occasional bright fireball that lights up the landscape.
Summer Observing Tips
- Fight the dew. Oregon summer nights can be damp. A dew heater controller and heater strips for your eyepieces and finder are worth having.
- Start early. Even before astronomical dark, the Summer Triangle is well-placed and planets (if any are up) are visible in twilight.
- Use low power for the Milky Way. Wide-field eyepieces and binoculars reveal the star clouds and dark dust lanes far better than high magnification.
- Sagittarius is best early in the evening when it is highest — by midnight it has dropped significantly from Oregon's latitude.
- Join us at Adair County Park. Check the schedule for HVA star party dates.