http://www.astropix.com/Pegasus1_Galaxy_Cluster.html
Click on the link to see a larger version with more information.
This image was shot over the course of two years, mostly because of weather and other projects that got in the way.
It's a stack of 37 frames with 4 hours 26 minutes total exposure at ISO 800 at f/6.3 with a modified Canon T3i (600D).
This is a medium compact cluster with a diameter of 6.3 degrees, located near the Pegasus – Pisces border. This image shows the center of the cluster with a field of a little less than 1.5 x 1 degrees.
Jerry