Wild Duck Cluster M11 Star-Hop with Binoculars from Altair

Before you observe

M11 is best seen in August and September, when Scutum is well placed in the evening sky. Under a suburban sky, the naked-eye limit is about magnitude 5. The cluster is about magnitude 5.8, so it sits just beyond naked-eye visibility. Binoculars are the right tool. Do not expect a bright, obvious glow. Expect a small, compact group of stars.

A 7x50 or 10x50 binocular works well. A 7x50 shows a wider field, which makes star-hopping easier. A 10x50 shows more stars but a narrower field. Both are wide enough to hold the cluster, which spans only 9 arcminutes (0.15 degrees). Rest your elbows on a table or a chair back to keep the image steady. Steady views make it easier to see the faint stars.

Move away from direct streetlight glare if you can, and give your eyes 10 to 15 minutes to adapt to the dark. Check that the southern horizon is clear, because the route passes low in the south.

Altitude by latitude

The highest point M11 reaches in the sky depends on your latitude. The figures below are its maximum altitudes above the horizon.

• At 35° N, the cluster reaches about 49°. It is high in the sky and easy to reach by star-hopping.
• At 50° N, the highest point is only about 34°. You need a clear southern horizon, and haze or dust near the horizon will weaken the view. Start your hop early in the evening, while the field is still well placed.
• At 35° S, the cluster reaches about 61°. It is the highest of the three positions, so it is the easiest to find.

Star-hop from Altair

Altair is the lower point of the Summer Triangle, a pattern of three bright stars that is prominent in summer evenings. The other two points are Vega and Deneb. Altair is the brightest of the three stars that form the lower point and is easy to identify by its brightness.

Step 1: Find Altair

Locate the Summer Triangle in the eastern to high sky during an August or September evening. Identify Altair as the bright star at the bottom of the triangle. Center it in your binoculars, and note the faint stars around it. You will use these as a reference when you move on.

Step 2: Hop to Lambda Aquilae

From Altair, move about 18 degrees toward the south-southwest. The direction is about 40 degrees west of due south. In a 10x50 binocular, 18 degrees is roughly three fields of view. Aim for Lambda Aquilae, a moderately bright star in the body of Aquila, close to the border with Scutum.

You do not need to follow a precise line. Sweep slowly, and when you reach a moderately bright star with faint neighbors, compare it with the star chart you are using or with a planetarium view. Lambda Aquilae should be the brightest star in its immediate area.

Step 3: Hop to M11

Center Lambda Aquilae in the field. M11 lies about 4 degrees to the west, a little south of west, roughly 20 degrees south of due west. That is about two-thirds of a 10x50 field. The cluster should appear near the western edge of the field when Lambda Aquilae is centered.

Move the binoculars slowly toward that edge, and check for a small, faint patch of light. If you see a diffuse cluster of points, you have found M11.

Checkpoint route through Alya

Alya is the brightest star in Scutum. It is a useful checkpoint because it lies close to M11 and is easier to recognize once you are in the right region.

From Lambda Aquilae, Alya lies about 5.5 degrees to the west-southwest. In a 10x50 binocular, this is a little less than one field of view. Center Alya, then look about 2 degrees to the north-northeast. M11 lies in that direction, a little less than one-third of a 10x50 field from Alya.

Use this route to confirm your position if the direct hop from Lambda Aquilae does not show the cluster. Alya's brightness makes it a more reliable reference than the faint stars around it.

Confirming you have arrived

Several features help you confirm that you have found M11 rather than an unrelated haze or a single star.

• It is a patch, not a point. Stars look like sharp points of light, even in binoculars. A cluster looks like a small, extended patch. When you move the binoculars slightly, the patch stays together, while a single star stays a point.

• It resolves into stars. Look carefully at the edges and the center. You should be able to pick out several individual stars. In a 10x50 binocular with good transparency, the brighter members form a loose wedge or V-shaped group. Under suburban light, you may see fewer stars, and the pattern can be faint.

• The surrounding field is sparse. M11 sits in a region that is not especially crowded with bright stars. If the area around the patch is crowded with bright stars, check whether you have centered on a star cluster or a different object.

• It stays in view. Hold the binoculars steady for a minute. The cluster should remain in the field, and its stars should become clearer as your eyes adapt.

If you see only a faint, featureless glow, return to Lambda Aquilae and repeat the hop more slowly. Dew on the lenses and haze near the horizon can both reduce contrast, so check those conditions too. If the sky is hazy, try another night.