The Little Star Cloud
By Shawn Grant
There has been times when the sky is so clear that when the milky way rises people pack it in because they think that it is clouds. The most concentrated part of the summer Milky Way is in Sagittarius. At a dark site the view is sometimes overwhelming. You see a mass complex of stars, nebula and dark nebula. The Milky Way is truly the best aspect of deep sky observing.
In Sagittarius there is a star cloud that is 1 degree by 30 minutes in size and is more compressed,
rich and detached from the rest of the Milky Way. This is M24. In the past there has been some disagreement over the identification of this object. Many people thought it was the cluster NGC 6603. With careful examination of Messier’s records revealed that he observed a cloud containing stars of various magnitudes that is 1 degree by a half a degree in size. NGC 6603 is a much smaller cluster within M24. Many charts and computer software still label NGC 6603 as M24. Disregard this because it is not accurate.
With binoculars M24 is a beautiful sight. The cloud comes a blaze with a mass of stars. You may quickly notice two pronounce dark nebula B92 and B93. M18 will be obvious to the north and the most concentrated part of M24 is NGC 6603. It is hard to tear away from such a great binocular view. When you are ready we will begin our detailed telescopic view.
When you first point your scope at M24 you will see a mind-blowing mass of stars. There are several 6th to 10th magnitude stars with a scattering of fainter stars and some haze. It will leave you breathless by its supreme beauty. It is rectangular in shape with B92 and B92 on the western side with another mass beyond that. The most heavily concentrated partition of M24 is NGC 6603. NGC 6603 is very rich and well detached even in the star rich region. It has very faint stars, about 75 13th magnitude or dimmer. I love rich open clusters with faint stars. The faintness of the stars gives the illusion of diamond dust. This is probably one of the prettiest areas of M24.
To the west of NGC 6603 is the open cluster Collinder 469. It is hard to pick out and is very poor in stars. I am not sure why it is considered a cluster at all. It is just a few stars that marks the edge of B93.
Dark nebulas have long been overlookedby amateurs. B92 and B93 are showpieces of dark nebula. The views of these nebulas will get you hooked on your lifetime exploration of dark nebula. B93 is the eastern most of the two. It is long and slender similar to a comet. It has a size of 15’ X 3’ north to south. B92 is to the west of B93. It is much more sharp and defined. It looks like a huge hole torn in the fabric of space. It has a size of 15’ X 7’ proceeding north to south.
At the southern edge of M24 lies a small but compact cluster Markarian 38 or Buir 5. The cluster
is small with a size of 2 minutes. A bright 7th magnitude star is the pinnacle of the cluster with a scattering of a dozen or so 12th magnitude stars. The cluster is truly a jewel that easily holds its own with the other gems near it.
Our last object in M24 is the planetary nebula NGC 6567. It has a brightness of 11th magnitude and a small size of 8 seconds. It is very hard to pick out because of the crowded star fields. You will need detailed charts to pick out the exact location of this nebula. Once you find it you will see a bright but small nebula that brightens gradually towards the center.
I am sure you will enjoy observing the wonders of M24. It is one of the most remarkable areas in the whole celestial sphere. It represents easy targets for beginners and deep sky challenges for the most accomplished veteran.