By letting pass 98% of H-alpha, H-beta and O-III emissions, this filter is idealfor astrophotography of nebulae allowing you to record images with a darker sky background. This filter is coated with various optical treatments to ensure better quality, such as the Multibandpass for better color balance without creating annoying dominants that are sometimes difficult to correct and the IGAD Ion Gun Deposition treatment, which provides hardness and guarantees an easier filter cleaning.