M45 - The Pleiades
2013-10-04 
See more information here for the night this picture was taken. 
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist. They are loosely bound to each other by mutual gravitational attraction and become disrupted by close encounters with other clusters and clouds of gas as they orbit the galactic center, resulting in a migration to the main body of the galaxy as well as a loss of cluster members through internal close encounters. Open clusters generally survive for a few hundred million years. In contrast, the more massive globular clusters of stars exert a stronger gravitational attraction on their members, and can survive for many billions of years. ― source and more information wikipedia
Date: 2013-10-04
Location: Ekerö, Sweden
Temperature: 8 °C
Telescope: Sigma 120-400mm APO HSM lens
Camera: Nikon D5100
ISO: 1600
Mount: Astrotrac mount and TW3100 wedge
Exposure time: 69 X 15 sec
Other info: Lens set at 400mm/F8.
Processing: Stacked and darks-subtracted in DeepSkyStacker. Processed in Photoshop CS6.