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Visual Deep Sky Observing: Star Clusters

By Edited Nov 19, 2016 0 0

The second section of my visual deep sky observing guide covers some of the prettiest objects in the night sky. These objects, open and globular clusters form the meat and potatoes of star cluster observation for urban and suburban deep sky observers as these objects are the brightest celestial objects in the night sky. Most of those listed below can be easily observed with the naked eye, even from very light polluted skies. They come alive in wide field binoculars and telescopes, appearing as jewels set against a dark velvet background. Listed here are the five of my favorite northern sky  examples.

M45, The Pleiades Cluster (Constellation: Taurus)

 

M45

The title of the brightest open cluster in the night sky belongs to M45, better known as The Pleiades or Seven Sisters. Although composed of more stars, most people can spot between five and seven of the brightest stars in this cluster with the naked eye, hence its nickname the seven sisters. Locating this cluster is simplicity itself, due to its easy naked eye visibility. It also happens to lie close to yet another excellent naked eye V shaped open cluster at the heart of the constellation of Taurus the bull. This cluster is best seen at very low magnifications and in binoculars. In fact to take in all of the cluster's members, its better to use a low powered instrument. I often find myself enjoying the views more in my 7x50mm finder than in my main scope. This very young cluster also has some reflection nebulosity around some of its brighter stars. This is a lot harder to spot and requires a very keen eye and very transparent skies. There have been reports of this nebulosity being spotted in instruments as small as a 7x50mm binoculars. 

NGC 869 and NGC 884, The Double Cluster (Constellation: Perseus)

 

Double Cluster

Yet another easy to spot open cluster, this object (or objects as it is composed of two open clusters) lies in a very rich region of the northern milky way at the head of Perseus, between this constellation and W shaped Cassiopea. From light polluted Los Angeles skies, I can make out the two splotches that form this cluster with my unaided eye. This rich cluster struts its stuff in binoculars and small telescopes. However to appreciate its beauty,  use low to medium power (under 50x magnification). As they are more condensed than M45, the cluster appears much prettier in binoculars and telescopes than with the naked eye. Best viewed from dark locations as many more of its dimmer members shine through.

M44, The Beehive Cluster (Constellation: Cancer)

This cluster is a borderline naked eye object, which requires darker and more transparent skies to be visible, since its component stars are fainter than M45. From white zone light polluted Los Angeles skies, this object is not visible to the unaided eye. From darker orange zone Malibu skies, it is much easier to see. To spot this object, try making out the dim constellation of Cancer, the crab. This in itself is hard as the stars that form this constellation are very faint. This cluster is yet another example of one that looks better at very low magnification. The wider the field of view the better. The best views come from binoculars and finderscopes!

M22, The Crackerjack Cluster (Constellation: Sagittarius)

 

M22

This globular cluster would be ranked as the best and brightest globular in the northern sky were it not located so far south in the constellation of Sagittarius. It does rise sufficiently high throughout most of continental USA. This bright globular is a naked eye object from darker skies and is fairly easy to locate. Firstly look for the teapot shaped constellation Sagittarius.  It is found just to the left of the topmost star of the teapot's lid. Its quite a pretty sight in 10x50 binoculars and in small scopes, appearing as a fuzzy grey cotton ball with no condensed core. Although it does not show resolution in smaller scopes, some of its stars are resolvable in 76mm scopes. This is one of the easier globulars to resolve as the stars have a bright horizontal magnitude. For best views, use high magnification in a 130mm or larger scope. 

M13, The Great Hercules Cluster (Constellation: Hercules) 

 

M13

Dubbed the king of the globulars of the northern sky, this object is also very easy to spot as it lies in the northern part of the constellation of Hercules. Just locate the keystone and the globular should be slightly south of the top-right hand most star. Like M22, M13 appears like a fuzzy grey snowball, but shows a denser core in small instruments. Partial resolution is possible at high magnification (in excess of 100x) in scope 150mm or larger. One of the reasons for its popularity is due to the fact that it lies almost overhead during the winter months. This greatly affects its resolution as there is less atmosphere to look through when one is looking straight up.

Summary

These are the best the northern skies have to offer in my humble opinion. There are several other equally compelling northern sky gems that are worth the mention. These include M6 and M7 in Scorpius (though these are better seen from the southern hemisphere as they do not rise very high in the sky)and M11, the Wild Duck Cluster in Scutum. The southern skies boast even bigger and better clusters. Most notable are globulars Omega Centauri (NGC 5139 ) and 47 Tucanae (NGC 104). The next time there is a dark of the moon, go outside and look up. The cosmos is there for the viewing!

 

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