3.5 nm FWHM (to harmonize the exposure time with O-III / S-II), recommended for fast optical systems from f/3.4 to f/2.3
Specially designed for the special filter requirements when used with fast f/3 optics
For highest contrast even at strongest light pollution, minimizes star size, emphasizes finest nebula detail – indispensable under Bortle 9/8/7/(6) skies
Reflex-Blocker™ hard coated and planeoptically polished – with sealed coating edges
Blackened edges all around, with filter-lead-side-indicator in the form of a telescope-sided black outer rim
Optimized for modern CMOS cameras, but likewise excellent for CCD camera technologies
For more information about, Baader H-alpha 50.4mm f/3 3.5nm Ultra-Highspeed-Filter website.