Open clusters are physically related groups of stars held together by mutual gravitational attraction. They are believed to originate from large cosmic gas/dust clouds in the Milky Way, and continue to orbit the galaxy.  Open clusters populate about the same regions of the Milky Way and other galaxies as diffuse nebulae, notably spiral arms in disk galaxies, and irregular galaxies, and are thus found along the band of the Milky Way in the sky.

Most open clusters have only a short life as stellar swarms. As they drift along their orbits, some of their members escape the cluster, due to velocity changes in mutual closer encounters, tidal forces in the galactic gravitational field, and encounters with field stars and interstellar clouds crossing their way. An average open cluster has spread most of its member stars along its path after several 100 million years; only few of them have an age counted by billions of years. The escaped individual stars continue to orbit the Galaxy on their own as field stars: All field stars in our and the external galaxies are thought to have their origin in clusters.

 Equipment Used

M36 - Auriga

This open cluster shows up as a faint grey smudge when viewed with binoculars.

A telescope clearly shows many stars in the cluster down to about 10 - 12th magnitude. Using a 24mm eyepiece you get a magnificent view of the whole cluster which is arrow shaped in appearance - it really is a jewel in the sky!

6" Reflector

24mm eyepiece  (32X Magnification)
 9mm eyepiece    (64X Magnification)

M37 - Auriga

This open cluster shows up as a faint grey smudge when viewed with binoculars.

This cluster is similar in appearance to M36 but is a lot brighter as it contains many more stars than M36. It's well worth a look. A telescope easily resolves the stars in this cluster.

M38 - Auriga

This open cluster shows up as a faint gray smudge when viewed with binoculars.

This cluster is similar in size to M36 but is reported to have the shape of a cross, I'm not so sure I could make this shape out but you can easily resolve the stars with a telescope.

M41 - Canis Major

As this cluster is quite low in the sky I couldn't make it out in binoculars due to the glow in the sky from light pollution.

With a telescope this shows up as a nice little cluster with the stars grouped quite close together. Its reported to contain over 100 stars! I saw much less than this.

M44 - Cancer

This cluster is best viewed in binoculars as it's so large. The best view I had of this was in February with no moon to spoil the view. It really was a breath taking sight. The contrast of the bright stars against a very dark sky was incredible. I've viewed this cluster many times and not it seen as well since - I'll keep trying.