For producing striking, high-contrast color CCD astrophotography of emission nebulae with a monochrome CCD camera, you should use extra-narrowband filters. The 1.25" Orion Extra-Narrowband Hydrogen-Alpha filter is one of a set of three filters.
This filter is fantastic. Not only does it provide more detail of Ha regions in nebula, it increases my imaging opportunities since I can now photograph these nebula even in full moonlight. I highly recommend it!