ALFCSNURD31

FCSETNU-RD31

Alpine Astronomical

The 31mm Baader 3.5/4nm Ultra-Narrowband Filter Set from Alpine Astronomical features three precision-grade filters recommended for optical systems from f/10 to f/3.5. The set includes H-alpha, O-III, and S-II filters optimized for CMOS sensor cameras and suitable for use with CCD sensors.None 3.5/4nm half width (to harmonize exposure time of H-alpha with O-III / S-II), recommended for optical systems from f/10 to f/3.5None Enables high contrast even with the strongest light pollution to minimize the size of stars and make nebula details accessible which is useful under a Bortle 9/8/7/(6) skyNone Reflex-Blocker hard-coated and optically polished, with Life-Coat sealed coating edgesNone Blackened edges all around, with a filter front indicator in the form of a black outer edge on the frontNone Optimized for CMOS sensor cameras and suitable for CCD sensorsNone FWHM on each filter category carefully designed to allow for 1:1:1 exposures, matched for typical CMOS quantum efficiency and s/n ratioNone 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