Filter Optolong H-Alpha 7nm 50x50mm Optolong · H-Alpha 7nm 50x50mm Key specifications Filter typeNarrowband PassbandHa 656 nm Bandwidth7 nm Filter sizeOther About Improved-version 7 nm H-alpha narrowband imaging filter centered on 656 nm; 50 x 50 mm square, 3.0 mm thick.