Targets for June 23–July 3, 2014
Small telescope: Open cluster NGC 6383
Small telescope: Globular cluster NGC 6229
Large telescope: The Cheerio Nebula
Easy cluster, crowded field
This week’s first small-telescope target is open cluster NGC 6383 in Scorpius. To find this object, look 4.5° north of magnitude 1.6 Shaula (Lambda [λ] Scorpii). Alternatively, find the Butterfly Cluster (M6), and look 1.2° to the west-southwest.
If this magnitude 5.5 cluster wasn’t in the same direction as the center of the Milky Way, it would be an easy naked-eye catch. It spans 20′, which means it covers 41 percent as much area as the Full Moon.
Once you spot NGC 6383, the first star you’ll see is magnitude 5.7 SAO 208977. That’s the luminary supplying most of this cluster’s brightness, but the faint stars around it contribute to the nice overall display.
Through a 4-inch scope at a magnification of 100x, the central part of NGC 6383 reminds me a little of the constellation Grus the Crane. One crooked line of stars winds northwest to southeast, and a small bar crosses that line at the south end. SAO 208977 lies at the intersection.
Two lesser-known clusters lie near NGC 6383. Slightly less than 0.5° east is magnitude 7.7 Trumpler 28. It measures 8′ across. Look 1° west of NGC 6383 for another, extremely sparse, open cluster, magnitude 8.8 Antalova 2.
A nice glob in the Hero
This week’s second small-scope object is globular cluster NGC 6229 in Hercules. This magnitude 9.4 object sits 4.8° east-northeast of magnitude 3.9 Tau (τ) Herculis. It measures 4.5′ in diameter.
At low to medium magnifications, you’ll see a nice triangle formed by the cluster, magnitude 8.0 SAO 46278 only 6′ to the west, and magnitude 8.4 SAO 46280, which sits 7′ to the southwest.
NGC 6229 lies 90,000 light-years away, so its individual stars appear faint. The brightest glow at only magnitude 15.5. Through an 8-inch telescope at 200x, you’ll see an unresolved spot with an irregular outline. Through a 14-inch scope, you’ll pick up about half a dozen individual stars, and the cluster’s face will appear quite mottled.
Good for your heart
This week’s large-telescope target is the Cheerio Nebula, a planetary nebula in Scorpius. It also goes by the designation NGC 6337.
This target, named for the breakfast cereal it resembles, lies inside the arc of stars that forms the Scorpion’s stinger. Specifically, you can find it 2° southwest of magnitude 2.7 Upsilon (υ) Scorpii. It glows softly at magnitude 12.3 and measures 48″ across.
Through a 12-inch telescope at a magnification of 300x, you’ll see a thin ring with a superposed star on both the northeastern and southwestern edges. A nebula filter such as an Oxygen-III really helps because it will dim the surrounding stars but not the nebula. Although this object has a low magnitude, its surface brightness is high.
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