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Home , Pleiades, R Scuti, Wild Duck Cluster

One Good Target With Some Other Sights Worth Seeing While You’re in the Neighborhood

August The (M11) with side trips to a marvelous red carbon and a nice little patch of nothing to look at

Tucked away in the tiny (The Shield), The Wild Duck Cluster (M11) is one of the finest open clusters in the sky, arguably surpassed only by the incomparable (M45). With an abundance of sparkling , a reasonably easy-to-find location, and that wonderful flattened-V shaped group at the edge, like the vanguard leading a flock of birds, M11 is a perennial favorite at summer star parties.

This month’s targets: Stars to mag 5 North at top

Discovered in 1681, M11 contains nearly 3,000 stars: over 500 of them range from mag 11 to 14, but there are many fainter ones, and a couple brighter ones that may be foreground stars. At a distance of 6,200 LY, it glows at magnitude 6.3 and covers an area 14’ wide – about half as wide as the full Moon. It’s made up primarily of blue-white stars, but there are a significant number of yellow members, and even some red giants. Its density is similar to that of a loose , making The Wild Duck one of the densest of all open clusters.

To find M11, start at mag 3.4 Lambda () Aquilae, which marks the tail of Aquila (The Eagle). Move your finder SW through 12 Aquilae (mag 4.0) to mag 4.8 Eta () Scuti. With Eta centered in the finder field, 12 Aql will be 1.2° to the east, and a mag 6.0 star will be directly opposite it, 1.8° west of Eta. M11 will be in the finder field, 1.6° WSW of Eta. Center the mag 6 star and M11 will be just 29 arcminutes to its SE. The mag 6 star and the one next to it are both wide telescopic doubles – 6.1 + 8.6 sep 114” and 6.5 + 9.8 sep 38” – and the one that forms a triangle with them is a variable yellow-orange giant, , ranging from mag 4.5 to 8.2. Binoculars will reveal the cluster’s roughly triangular shape, but there is no resolution of individual stars, although it will appear brighter towards center. M11 begins to resolve in small to medium , revealing many groups of bright stars separated by twisting dark lanes. Start at medium power, 75x or so, and increase from there: the cluster will stand up to as much power as local seeing conditions will allow.

5° fields, North at top, stars to mag 7.5 (L) 8.0 (R), selected magnitudes shown, decimals omitted

While you’re in the neighborhood, point your finder at the space between Lambda and 12 Aquilae, and look just to the SE (or follow a short arc of stars looping away from 12 Aql) to find the deep red color of V Aquilae, one of the best carbon stars in the sky. Like all carbon stars, it’s a red supergiant whose crimson hue is enhanced by the presence of carbon molecules in its atmosphere, which scatter light at the blue end of the spectrum and allow the red light to pass through. Its color becomes less intense as the star brightens, but its narrow range (mag 6.6 to 8.4) keeps it well within view in any , and most binoculars, even when it’s at its faintest.

Before heading home, drop your gaze a little farther south to find one of the sky’s finest examples of nothing to look at. Dark B133, an oval measuring 10x5 arcminutes, is an area of interstellar dust and gas so dense that it blocks our view of the Milky Way. In fact, a four hour photographic exposure through the 100 inch telescope at Mount Wilson showed no visible stars whatsoever in this area. Look for a small, inky black silhouette 2° south of Lambda Aquilae, 1.2° WSW of a mag 6.8 white star with a faint red companion – the nebula forms a right triangle with Lambda and 12 Aql. It can be seen in binoculars, but is easier in a telescope due to its relatively small size. When you say “I don’t see anything,” you’ve found it! And if you enjoyed hunting down B133, see if you can spot a few of the many dark that surround M11, as shown on the chart at right. Happy hunting! Dark Nebulas near Cluster M11 Rick Gering / August 2020 [from Uranometria 2000.0]