Barnard's E is a large dark nebula that lies very close to the bright star called Altair which is the most southern star in the summer triangle. This dark nebula is really dark dust that obscures the rich blanket of stars behind it in our own milky way galaxy some of which just poke through the dust. An upper case 'E' tilted back to the left on it's top is seen in this picture that covers 1.5 degrees from left to right. This dark nebula is visible with binoculars from a very dark site.