Filter · MSRP $193 Optolong H-Alpha 7nm 36mm Optolong · H-Alpha 7nm 36mm Key specifications Filter typeNarrowband PassbandHa 656 nm Bandwidth7 nm Filter size36mm About Improved-version 7 nm H-alpha narrowband imaging filter centered on 656 nm; 36 mm diameter, 2.0 mm thick.