This 31mm round, unmounted Baader 4nm f/2.0 Ultra-Highspeed O-III CMOS Filter from Alpine Astronomical is recommended for extremely fast optical systems from f/3.4 to 1.8, and is designed for the special filter requirements of fast optics like Celestron RASA astrographs. The filter features a Reflex-Blocker hard coating, which has been planoptically polished, and has Life-Coat sealed edges. It is equally suitable for modern CMOS sensors as well as for older CCD camera technologies.
- 4nm FWHM, recommended for extremely fast optical systems from f/3.4 to 1.8
- Specially designed for the special filter requirements when used with fast optics like the Celestron RASA astrographs
- Reflex-Blocker hard coated and planoptically polished with sealed coating edges (Life-Coat)
- Blackened edges all around, with filter-lead-side indicator in the form of a black frontside outer rim
- Optimized for modern CMOS cameras, but excellent for CCD camera technologies