H-Beta Filter

The only way to see the Horsehead Nebula and the California Nebula. This filter is so specialized, it is really only good for two objects; IC 434, the emission nebula surrounding the Horsehead Nebula in Orion, and the California Nebula. Both of these objects emit strongly in the hydrogen beta portion of the spectrum. While it is possible, just barely, to catch a glimpse of the Horsehead without the H Beta, the view with it is far more stunning. The filter emphasizes the glow of both of these nebulae, turning them red. (Source: sciastro.net)