The DGM Optics HPOIII is your perfect compliment to the NPB when you need a more aggressive Nebula filter that really shines with larger scopes. This filter has a bandwidth of approx. 15nm for those faint, elusive objects, but also has a feature that most other OIII filters don`t with high transmission at H-Alpha. For a visual OIII filter this is important as it provides a bit more "optical throughput" than leading competitors. As with all DGM Optics filters durable Ion Assisted Plasma Coating Technology ensures an ultra-hard, low scatter coating.