CCD Astrophotography - Dark Nebulae

In addition to the previously mentioned forms of nebulae (see Nebulae) there also exist Dark Nebulae. Such nebulae appear as dark areas, containing few if any stars. They are due to interstellar dust between us and the background stars. When this interstellar dust protrudes into an area of nebulosity the dark areas are more contrasted and are sometimes evident as intriguing shapes and figures. E. Barnard compiled a catalogue of such nebulae. The Horsehead Nebula (B33) is one such nebula, which consists of a dark dust cloud projection, in the shape of a horse's head, into a region of bright nebulosity (IC 434) near to Zeta Orionis in the constellation of Orion. The imaging of these nebulae by amateurs is notoriously difficult because of the poor contrast. Even with good seeing and reasonable image scale special filters are usually desirable. However,occasionally an image can be obtained without such niceties as evidenced below. On a clear but very cold night, following collimation checks, two 3 minute images were taken to give the following image of the Horsehead Nebula.