Photographs of the night sky made in the deep-red light of H-alpha emission (at a wavelength of 6562.8 angstroms) highlight the glowing clouds of hydrogen gas that permeate our Milky Way galaxy. Many of these brighter clouds, such as the North America Nebula, the California Nebula, and the Lagoon Nebula, are well-known objects and have been popular astrophotography targets for more than a century. But deep, wide-field, H-alpha photographs reveal a vast network of fainter, wispy filaments of nebulosity strewn across the sky. These views are analogous to stepping back and looking at the whole forest rather than just the individual trees.
Low-resolution maps of this huge network of hydrogen emission have been made by various means, including radio telescopes, emulsion-based photography, and small-scale digital imaging. The purpose of the MDW Survey is to map this material with high-resolution digital images that, in part, will create a stunningly detailed picture of the glowing hydrogen in our galaxy. At the same time it will be scientifically useful and aesthetically beautiful – a true blend of science and art.