Compare Candy’s image to a portion of one of Barnard’s charts, posted below. This chart shows the positions of the region’s dark nebulae. The B in the object designations stands for Barnard. So, for example, the Snake Nebula (B72) was the 72nd object he cataloged.
Paolo Candy’s image of the Snake Nebula (B72) on page 120 of the January 2006 issue of Astronomy reveals an area rich in both bright and dark regions. Dark nebulae are clouds of dust and cold gas that block light from more distant stars, creating visual voids in space.
The most famous chronicler of dark nebulae is American astronomer Edward Emerson Barnard (1857-1923). Barnard compiled photographs of the Milky Way from which he cataloged 349 dark nebulae in Atlas of Selected Regions of the Milky Way. This work appeared in 1927.