B33/NGC 2024 - The Horsehead and flame nebulae
The Horsehead nebula is a dark nebula situated next to the bright star Alnitak, the left most star in Orion's belt. It is situated about 1500 light years from earth. It can not be seen with the naked eye unless one uses a very large telescope and a special filter. The flame nebula is an emission nebula visible in the same wide field as the Horsehead. One can see the location of the two nebulae in this 200 mm photograph of Orion:
Since one can not readily see the Horsehead nebula one has to use the starfield to compose the image. Fortunately, Zeta Orionis makes it pretty easy. This photograph was taken using a modified Canon T3i set at ISO 800 and a six-inch F-5 reflector. The resultant image is a stack of six five-minute exposures. The Horsehead nebula is the dark nebula to the right of the bright star Zeta Orionis (Alnitak). The other nebula, NGC 2024, is below Zeta Orionis.