In our lust for appreciating and recording bright and interesting celestial objects like galaxies, globular and open star clusters and reflection and emission nebulas, I think we too often overlook Dark Nebulas which are themselves, very interesting and beautiful objects.
Dark nebulae are tough objects to find, observe, image and process effectively. These are objects with large amounts of interstellar dust that are dense enough to block out much of the wavelengths of the visible light behind it. I enjoy observing them and I try imaging them when I can. The main catalog for these kinds of objects was created by American astronomer Edward Barnard more commonly known as E.E. Barnard. He catalogued many of these items in the “Barnard Catalogue of Dark Markings in the Sky” otherwise known as the Barnard Catalogue. The version of his catalogue published in 1927 shortly after his death listed 369 objects.
One of the most common dark nebulas imaged is of Barnard 72, known as the Snake Nebula. This object is in the constellation Ophiuchus and is a dust lane that snakes (pun intended) in front of star clouds of the Milky Way. This object is part of a much larger complex known as the Dark Horse Nebula; a very large dark nebula that exists as part of the central bulge of the Milky Way known as the Great Rift.
The largest dark nebula is Caldwell 99, more commonly known as The Coalsack. This object is in the Southern Hemisphere and you don’t need binoculars to see it. Just look for the Southern Cross and then at the bright south pointing star of Acrux in this constellation. It looks like the band of the Milky Way has a huge hole in it. Interestingly, this object is not listed in the New General Catalogue or in the International Catalogue - the only identification is in the Caldwell Catalogue (Caldwell 99), a catalogue of 109 objects compiled by Sir Patrick Moore, an amateur astronomer in the UK as a complement to the Messier catalogue. Another fine dark nebula example is Barnard 22 in Taurus.
The band of the Milky Way has a wealth of these objects. Messier 24, the Sagittarius Star Cloud is a fine example. It is a huge cluster of stars thousands of light years along our line of sight which you can see with the naked eye.