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Summer Observing Targets for Large Telescopes

Astronomy magazine Editor David J. Eicher shares 10 of his favorite summer deep-sky objects, including the Bug Nebula (NGC 6302), the Eagle Nebula (M16), Barnard's Galaxy (NGC 6822), and more.
RELATED TOPICS: DEEP-SKY OBSERVING
The Bug Nebula (NGC 6302)
One of the strangest nebulae known makes a good target for large scopes. The Bug Nebula, also known as NGC 6302, is a bipolar nebula in Scorpius with a strange, flattened shape set in a rich starfield. Shrouded in dust, the object consists of a dying star that is obscured within the bright disk we see, surrounded by the nebulosity belched off the star in several episodes. The result is an hourglass shape that you'll see quite well in a 10-inch scope under a dark sky.

The Bug lies about 3,000 light-years away and spans about 2 light-years across. The weird morphology of the Bug Nebula wasn't known until relatively recently, in a long history of study that dates back to Edward E. Barnard observing the nebula in 1907.
Open cluster NGC 6520 and dark nebula B86
Two-for-one objects are nice because they give you contrasting objects set together in a single field of view. One of the best for large scope observers lies in the thick of the summer Milky Way in Sagittarius. The bright open star cluster NGC 6520, a binocular object, lies within the same low-power field as Barnard 86, a prominent and oddly-shaped dark nebula.

Explore the star cluster at low power to see several dozen stars in a group measuring just 6 arcminutes across, with the brightest stars glowing dimly at magnitude 8. You'll see the dark nebula as a wedge-shaped area of inky blackness adjacent to a relatively bright field star.
The Eagle Nebula (M16)
The Eagle Nebula in the constellation Serpens, M16, will always be remembered for that celebrated "pillars of creation" image created with the Hubble Space Telescope. But it's an iconic object for large-scope observers, as there's so much detail to observe within the object in so many different ways. Like most emission nebulae, the Eagle is a large star-forming region in which the recycled gas and dust is gravitationally contracting into newborn stars, as evidenced by the cluster NGC 6611 embedded within it. A 10-inch or larger scope will have no trouble showing a large area of gray-green, gauzy nebulosity spread over the cluster and the most prominent towers of dust set against the backdrop. The whole complex lies at a distance of about 7,000 light-years and spans more than 100 light-years across.

Use a low-power eyepiece to explore the region before cranking up the magnification to examine specific features. By nudging the field around here and there and using averted vision, looking with the side of your eye's field of vision, you can capture the most delicate features that glow most weakly. You'll see some little dark knots of dust here and there, which are in reality gargantuan blobs of dust coalescing into protostars.
The Dumbbell Nebula (M27)
Planetary nebulae are great for summertime observing because they offer a nearly infinite variety of shapes and sizes. One of the most well-known is the Dumbbell Nebula in Vulpecula, and even if you're a large-scope observer who has seen the Dumbbell many times with a smaller scope, there's plenty to draw you back.

The nebula's curious shape, like a dumbbell or apple core, floats symmetrically over the 14th-magnitude central star. You will no doubt see a sprinkling of stars scattered across the nebula's face, as well as hints of the faint, outer "ears" of nebulosity that, with a big backyard scope, close the shape into a near circle. This delicate nebula floats at a distance of 1,400 light-years and spans about 2 light-years across.
The Gamma Cygni Region
One of the richest areas of summer Milky Way stands tall overhead in Cygnus, near the center of the constellation's great cross shape. The star at the center of the group is Sadr, Gamma Cygni, a 2nd-magnitude beacon.

Surrounding the area of Sadr is a network of emission nebulosity that is one of the most complex and fascinating in the sky. Over an area of several square degrees, on all sides of the star, are patches of nebulosity catalogued as IC 1318 and IC 1311, the brightest portions immediately east and northwest of the star. These glowing regions are really tough to see, as they are large and have low surface brightnesses. Large scopes will reveal them, however. To succeed, use a low-power eyepiece and slowly and carefully scan around the area.
Spiral galaxy NGC 6946
With the Milky Way dominating the summertime evening sky, galaxies are few and far between. But there are so good ones placed well, a leader being NGC 6946 in Cepheus. Sometimes called the Fireworks Galaxy, this object is a beautiful, face-on spiral with knotty arms that can be seen readily with a large scope.

At a distance of 18 million light-years, NGC 6946 is relatively close, enabling it to shine pretty brightly at magnitude 9 and extend over an area of 11 by 10 arcminutes. Despite the fact that it lies close to the galactic plane in a very rich starfield, you'll really enjoy carefully studying the galaxy's spiral arms. The details - knots, clumps, star-forming regions, dark lanes - are fantastic.
Globular cluster M22
In the springtime video I described a favorite globular cluster, M13. This time I'll turn to another "killer" cluster that no one should miss seeing this summer, M22 in Sagittarius. One of the repositories of the galaxy's oldest stars, M22 contains half a million yellowish, aged suns that have been around for as long as the Milky Way. It lies 10,000 light-years away, measures 100 light-years across, and would be one of the sky's greatest showpieces if not for the fact that it's so close to so many other bright Messier objects.
Barnard's Galaxy
Here's another summertime galaxy, although unlike NGC 6946, this one is a real challenge to see at all. Barnard's Galaxy, NGC 6822, is so faint and obscured by the plane of the galaxy that it went undetected until 1882, when Edward E. Barnard spotted it with a 6-inch refractor. To do that, however, you will need an extremely dark sky. The galaxy's southerly declination in Sagittarius means most North Americans need ideal conditions to place it high enough over the horizon to see well.

Although the galaxy glows at magnitude 9 and covers 10 arcminutes, its density is so poor it appears like an extragalactic ghost. An irregular galaxy lying only 1.6 million light-years away, Barnard's Galaxy is a member of the Local Group, one of those small, poorly populated galaxies we wouldn't even see from afar.
The Veil Nebula (NGC 6960)
If Barnard's galaxy gave you a terrific challenge, you'll find some relief in the Veil Nebula, the most spectacular supernova remnant visible in Earth's sky. The Veil is a large nebular complex that consists of several pieces, the two main ones being edges of the explosive arc thrown off by the now-destroyed star. The westernmost arc, NGC 6960, is shown here and appears to cut across the 3rd-magnitude star 52 Cygni.

Few objects are as well tailored to large scopes as the Veil Nebula. The eerily glowing, gray-green light of the nebula appears like twisted, fibrous rope on nights of good transparency. Use a low-power eyepiece at first and then switch to high powers to examine this intricate structure.
Planetary nebula NGC 7008
We saw a bright, very detailed planetary nebula in the Dumbbell. Now consider looking at a planetary, nearby in Cygnus, that is a weird, misshapen wreck. NGC 7008 is faint, glowing at 13th magnitude, but also large, spanning more than an arcminute across. Two bright stars near the edge of this nebula and several stars sprinkled within it, including the 13th-magnitude central star, give the field a strange look. See if you can detect a sort-of flattened egg shape, with a concentric shell or two inside the outer halo.
We've created two more videos like this one to help you enjoy everything the summertime sky has to offer. Astronomy magazine subscribers have access to Senior Editor Michael Bakich's video "Summertime observing for small telescopes." This video highlights the best summertime targets you can see with 4-inch or smaller telescopes. And Astronomy magazine Senior Editor Rich Talcott's video "Naked-eye summertime observing, 2009," highlights the best summertime targets you can see without optical aid.

There you have it, some of my favorite deep-sky objects for large scopes after 30 years of observing. Be sure to let me know about your favorites by emailing me at editor@astronomy.com. For more about Astronomy magazine, see astronomy.com. Until next time, I'm Dave Eicher, and thanks for watching — I'll see you out under the stars.
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