Open Cluster

Open Clusters are the remnants of a burst of stellar birth. Almost all the stars in the cluster are about the same age, although they may vary widely in brightness and color. Most clusters have a core group of bright stars and many dimmer members. Clusters represent the childhood and early adolescence of a stars life cycle. As the stars age they will drift apart since they are not normally gravitationally  bound as  the stars in a Globular Cluster. Open Clusters are also known as galactic clusters since they are within the galaxy. As before they are "Open" as in not bound and the members do drift apart as the cluster ages.

M46 and NGC2438. The Cluster is Messier 46 and is easily seen in binoculars in the constellation of Puppis. The small violet and white puff of smoke is NGC 2438 and is a planetary nebula. The term planetary nebula was used by William Herschel and refers simply to an object that looks like a planet (small disc) in his telescope. Photographs reveal the intricacies of this and other planetary nebula such as M57 and M27. As discussed earlier Clusters are composed of young stars. However a planetary nebula is formed at the end of a stars life. How is it then that a planetary nebula is in an open cluster? Well it isn't , this is a perfect example of the fact that the Universe is 3 dimensional, The planetary nebula is actually much further away than the cluster and happens to be in the same line of sight. So in this one shot we have the youth and senility in the life cycle of stars.

The bright star and vertical streak in the lower right is due to 'blooming'. The CCD camera used does not have an Anti-blooming gate to drain off excess charge. So when the CCD pixel reaches a full charge the electrons overflow into to cells around it resulting in the spike when it is processed. There is also a satellite trail in the upper right of this picture.
The Double cluster in Perseus is a fine case for the resolving power of different astronomical instruments. To the naked eye it appears as a smudge or cloud. A pair of binoculars reveals that it is two clusters. And finally the telescope reveals the true structure of the detail. This is an images composed from 10 L RGB 1 minute images.

 
The Cluster M35 is in Gemini. It is a very large and easily seen in binoculars. There is a small cluster in this photograph, titled NGC 2158. While it is small in appearance this is a illusion since this cluster is very far away in comparison to M35. In fact precise measurements indicate it is similar to M35.
M103 is a small cluster in the rich target area in Cassiopeia. This tiny cluster in medium telescopes with medium magnification appears to me look like a Christmas tree lit up in the night with a string of multiple lights. I don't know of anyone who calls it that but for me and I hope you it will become one of your favorite "overlooked" objects.

 
This is M45 also known as Pleiades, Subaru and perhaps many other things in different languages. It is easily the brightest  open cluster in the night sky and is visible from almost anywhere  on the earth.  There are 6 easy to see stars and others with good eyesight can make out 7 with the unaided eye. The blue reflection nebula is essentially dust and gas that are remnants from the nebula that the stars formed in. In the past trying to capture the blue nebula was a challenge due to the large dynamic range from the very bright  stars to the very dim nebula. It was difficult for film to capture this without special processes. A CCD camera with it's sensitivity and  ability to "sum" images from one frame to another makes this easier but now the challenge becomes trying to capture all the nebula accurately. Close inspection of the nebula will show that it is varying in intensity and color. There are brownish areas in the lower part and channels inside the nebulosity itself.