This 50 x 50mm Square, Unmounted Baader H-beta Narrowband Filter, from Alpine Astronomical, is a 5.5nm FWHM filter recommended for optical systems from f/10 to f/3.5. It features a Reflex-Blocker hard coating, which has been planeoptically polished, and has Life-Coat sealed coating edges. It is equally suitable for modern CMOS sensors as well as for older CCD camera technologies.
- Reflex-Blocker coatings offer largest ever freedom from halos, even under most adverse conditions concerning aux-optics
- Identical filter thickness to existing standards (2mm), with utmost care for parfocality
- Blackened edges all around, with filter-lead-side-indicator in the form of a black frontside outer rim, to additionally eliminate any reflection due to light falling onto the edge of a filter
- Each filter coated individually, with sealed coating edge (not cut out of a larger plate with coatings left exposed)
- Life-Coat: evermore hard coatings to enable a non-aging coating for life - even in a most adverse environment