Messier 103 is an open star cluster in Cassiopeia. It contains a few hundred stars that are around 10,000 light years away. This image is composed of 413 four-minute exposures, giving almost 28 hours of total exposure. There are 46,441 stars in this image. There is also some interstellar dust visible. The line towards the top left is a diffraction spike from the star Ruchbah.