Open Clusters

Unlike globular clusters, open clusters are relatively loose collections of nearby stars. Also, unlike globular clusters they tend to be within the disk of our galaxy rather than in a halo around it like globular clusters. From a photographic perspective, I don’t find them very interesting - They just look like slightly more aggregated stars than you will see anywhere you look in the sky. Quite a few of the Messier listings as well as the NGC catalogue are open clusters, however. Not wanting to ignore them completely, there are a couple that stand out from the crowd a bit.

The double cluster in Perseus

The somewhat denser cluster on the left of the picture is catalogued as NGC869 whereas the looser cluster on the right is NGC884. The image is a rather large area in the sky (bigger than the diameter of the full moon). This image was taken with a 150mm Newtonian telescope.

M35

This cluster is also visibly a double cluster. M35 is the loose aggregate of stars to the lower left of the figure. The denser group of stars to the upper right is not considered to be part of M35 but is assigned the designation NGC2158. In fact, the two clusters are not near each other in space, M35 is about 3000 light years away, while NGC2158 is about 11,000 light years away. This image was taken with a 150mm Newtonian.

NGC 2158

This is a close up of a portion of the sky seen in the photo above taken with the 16” Cassegrain telescope at the observatory. It is sort of an “almost” globular cluster.