It’s summer, and time for country folk to head to the big city. We’ve been out bailing hay in deep space too long, and the bright lights of the summer Milky Way are calling. Lots to see and do: endless clusters, nebulae, star fields, you name it. No downtown bus tours available here, but we do offer a small glossy with a few highlights noted. Be sure to also bring your own map though; there’s always plenty of interest on those hidden back streets. Enjoy!

NGC 6281 rating EASY
   open cluster in Scorpius
   RA 17h 04.8m  Dec -37d 54.2′  (2000)
   Magnitude 5.4

Southeastern Scorpius, particularly in the vicinity of the tail and stinger at Lambda Sco, is a region swarming with open clusters stretching along the central Milky Way. One of these is the binocular cluster NGC 6281. It was not included in either the Messier or Caldwell catalogs, but it is the brightest cluster in Scorpius to be left out of both.

NGC 6281 is visible visually:  to find it, move your eyes or binoculars due east along a line extending from the 3rd magnitude pair Mu Sco, in the body of the Scorpion, toward the Scorpion’s stinger at Lamba Sco. You’ll find the cluster roughly 1/4 of the way along this line, or about 2 degrees east of Mu. In binoculars it appears as a tight swarm of 7th- to 9th-magnitude stars.

A 2.4-inch scope will show you a pretty cluster of about 20 stars arranged like Christmas tree lights over a background haze, and a wide pair including the brightest star on the NE side.

Large scopes, like a 12-inch, will show a cluster with a rough teardrop shape, and the above pair at the pointed tip of the drop. You can pick out about 30 stars, many 11th magnitude and fainter, visible in the 7×6′ area with no hint of haziness and plenty of space between the stars.

NGC 6281 has a radius of about 26 light-years and a total of about 214 solar masses.


M69 rating MEDIUM
   globular cluster in Sagittarius
   RA 18h 31.4m  Dec -32d 21.0′  (2000)
   Magnitude 7.6  dia 7.1′

The constellation of Sagittarius, in addition to hosting the center of the Milky Way, also contains 15 Messier objects, all of which are clusters of one kind or another, and a few of which are also associated with nebulae. Of these 15 Messier objects, 7 are globular clusters. Of these 7, just 3
reside in the boundaries of the familiar Sagittarius “teapot”: M54, M69 and M70. And of these 3, only M69 hasn’t been targeted yet in this column, so this month we rectify that.

M69 is one of the smaller and fainter globular clusters in Messier’s catalog. It can just be seen in a dark night with 7×50 or 10×50 binoculars. It looks similar to nearby M70 in a 2.4-inch refractor. In a 6-inch scope at 100x it is unresolvable, but at 200x you can begin picking up outlying stars. A
10-inch scope will show you a nearly stellar nucleus, and you can partially resolve the cluster at 200x. In larger scopes, M69 is the easiest of the 3 Messier “teapot” globulars (M54, M69, M70) to resolve into stars; just be sure to use high magnification.

M69 has a diameter of about 70 light-years. It lies about 29,700 light-years away and is a close neighbor of M70; just 1800 light-years separate the two clusters. Both of them lie close to the galactic center, at roughly 6000 light-years.

M69 is unusual for a couple of reasons:  first, it’s one of the most metal rich clusters known – keeping in mind that to astronomers, a “metal” is anything heavier than helium. Second, it has almost no variable stars; only 8 are known, 2 being Mira-type variables with periods of about 200 days. By the way, if you’re curious, the other two Messier “teapot” globulars were our targets in July, 2007 (M54) and July, 2015 (M70).


NGC 6334 rating HARD
   nebula in Scorpius
   RA 17h 20.5m  Dec -35d 43.0′  (2000)
   Magnitude 8.9

NGC 6334 is a Milky Way emission nebula that’s located about 3 degrees NW of Lambda Sco (Shaula), the first magnitude star that marks the Scorpion’s stinger. Also cataloged as Gum 61-64, the nebula has been dubbed as both the “Cat’s Paw Nebula” and “Bear Claw Nebula.”

The Cat’s Paw is one of the nearest HII regions to our solar system. It lies about 5500 light years away and is a large star-forming region about 50 light years across, covering an apparent area of the sky slightly larger than the full moon. It contains a vast supply of material needed for star formation, roughly equal to a mass of 200,000 Suns. Consequently it is one of the most active stellar nurseries in the Milky Way, producing new stars at a more rapid pace than the more famous Orion Nebula (Messier 42). It probably contains tens of thousands of stars, many concealed by the nebula’s dust.

Although it was discovered in 1837 by John Herschel observing from the Cape of Good Hope in South Africa, today the nebula is much more popular as a photographic target than a visual one. While there are countless web links to beautiful images of the nebula, visual descriptions are few and far between.

One visual observation, using a 15-inch and OIII filter in dark skies, calls the parts of the complex very faint, with no easy targets. The only details visible are said to be “faint structureless patches of light,” and the the nebula is described as generally “unspectacular and difficult.” So it’s probably best to save the Cat’s Paw for your digital imaging equipment, unless you’re one of those intrepid explorers really into faint fuzzies.