Finding M11

M11: Open Cluster in Scutum

M11 is my favourite open cluster, and when you find it you’ll see why. It is quite different in character from all the others – very rich in stars and quite compact, so the effect is of a uniformly dense glow. It could easily be mistaken for a Globular Cluster.

Unfortunately, it is probably the hardest to find of the objects in my list of recommended objects for beginners, because there are no bright stars conveniently located nearby. So, you will need to have a fairly dark sky in order to pick out the finder stars in the constellation Aquila. It is worth the hunt.

Open clusters are easy to find and observe in small telescopes, pretty, and scientifically important. This is a group of stars all born from a common cloud of gas and dust. Since they came from the same gas cloud they are, astronomically speaking, all about the same age and all about the same distance from us, and they all started with about the same chemical composition. Knowing that they are the same age and at the same distance, the fact that they have different appearances allows us to learn a great deal about stellar evolution – the different appearances can only be a result of the different masses of the different stars.

Finding M11

Use the Summer Triangle to find the constellation Aquila, with its bright star Altair. (Here are detailed instructions to find the Summer Triangle.)

Now let’s look at the constellation Aquila more closely.

Note the two stars that form the Eagle’s head or beak. (Their names are not important, they are just listed here to provide a convenient label.)

Next, note another dim star just off the end of the Eagle’s head. It is so close that it looks like it should be part of this constellation.It isn’t – it is part of the nearby constellation Scutum, and its name is Eta Scuti.

Imagine a line drawn from 12 Aquilae to Eta Scuti.

Now, extend an imaginary line in that direction, the same distance again.

Point your telescope just to the right of the end of that line.

If you have a magnifying finder, you should be able to see m11 in the field, as a smudge of light that is obviously not a star.If you don’t have a magnifying finder, use your lowest magnification, widest-field eyepiece in the telescope to hunt for the smudge.

Carefully centre the object, then select an eyepiece that gives you 25x to 50x magnification.This simulated view shows the size of M11 in my 105 mm4-inch refractor at about 25x magnification.

All the above images were generated with Starry Night Pro.