M13 is a globular cluster visible to the unaided eye on the side of the "keystone" shape in Hercules. Its several hundred thousand stars are among the oldest in our galaxy. The density of stars in its central region is about 500 times greater than the neighborhood surrounding the sun. M13 is about 145 light-years in diameter and about 25,000 light-years away. The tiny galaxy visible near the top edge to the left of center is IC 4617, a 15th magnitude spiral galaxy that is perhaps another 10,000-20,000 times farther away.
More detail from the same image is shown below.These images are at the same scale as the images of globular clusters M2, M5, M15, M71, and M92.
152 minutes luminance and 144 minutes RGB using a QSI 583 camera through an Astro-Physics 155 mm refractor at f7.1 on 2011-07-06 and 2011-08-30 from northern New Jersey. North is up. ©2011