The astronomer Edward Emerson (E.E.) Barnard published a list of 369 dark nebulae known as the Barnard Catalogue of Dark Markings in the Sky. A great free link to a scanned version of his book is here.  

These nebulae were once thought to be holes in the Milky Way. After further study, they were discovered not to be holes but interstellar dust clouds which block the background Milky Way stars from our view.   The 369 dark nebulae vary tremendously in their density, size and beauty.  I have selected 25 images here which are my favorite.  These 25 images are comprised of 46 Barnard dark nebulae.

The technical data for the nebulae of the poster are shown in the attached table, including the field of view size.  Note that this size varies widely for the 25 images, from 10 to 180 arc-minutes.   

If you would like to read more about any of these objects, each of the objects in the poster has previously been uploaded and described individually on Astrobin. They all reside in my Barnard Dark Nebulae Collection.

This effort is part of the work currently being compiled in my upcoming eBook, which I will make freely available upon completion.

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Here is some information I found interesting about E.E. Barnard at the website linked above:

Born at Nashville, Tennessee, on December 16, 1857, he had little opportunity for education, owing to poverty. The mystery of the starry heavens caught his attention as a lad, and almost his first purchase beyond actual necessities was a telescope with which he might penetrate farther into the illusive study of the details of the nocturnal sky. As a small boy and until young manhood, he supported himself by working at Nashville in a photographic establishment in which he learned all the details of the art, an invaluable preparation for the future application of this knowledge to the celestial field. He discovered many comets, nebulae, and other objects of interest, with his small visual telescope, and later took courses at Vanderbilt University. He made such a name for himself that he was called to be an astronomer on the staff of the Lick Observatory at its inauguration in 1888. This brilliant period of discovery and observation continued until 1895 when he came to the University of Chicago to be an astronomer at the Yerkes Observatory. Here he labored with extraordinary assiduity and with distinguished success, from the opening of the Observatory in 1897 until ill health put an end to his observations at the close of 1922.  He died in 1923 at the age of 65.

Barnard was known as "The Man Who Never Slept."   He was one of the greatest astronomers of the 19th century. His exceptional eyesight aided him in the discovery of the fifth moon of Jupiter, approximately thirty comets, and numerous bright and dark nebulae. His lasting legacy is the set of exquisite photographs in his Atlas of Selected Regions of the Milky Way.  His perfectionism made it difficult for publishers to reproduce prints to Barnard's satisfaction. Barnard personally inspected each print. This meticulous care resulted in his highly regarded Atlas. Barnard did not live long enough to complete the text, so his niece (and twenty year associate), Mary Calvert handled the last aspects of publishing the Atlas.