This nebula is located in Orion. The area is dominated
by interstellar hydrogen glowing under the radiation
from the bright star in the middle of this image, but
there is also some gas that is simply reflecting the
starlight, and appears faintly blue.

Telescope: Hyperion 12.5"
Camera: SBIG STL-11000
Exposure: 16 hours (8 1/2 hours hydrogen-alpha, 7 1/5 hours RGB)