Baader SII CMOS f/2 Highspeed 2" This 2-inch S-II filter is the 6.5 nm f/2 Highspeed version from Baader’s CMOS-optimised Precision Grade range. It isolates the S-II emission band for narrowband imaging, with the manufacturer’s wavelength reference at 671.7 nm.
Manufacturer model: Baader SII CMOS f/2 Highspeed 2" · Specifications checked against manufacturer data on 2026-11-04
This 2-inch S-II filter is the 6.5 nm f/2 Highspeed version from Baader’s CMOS-optimised Precision Grade range. It isolates the S-II emission band for narrowband imaging, with the manufacturer’s wavelength reference at 671.7 nm.
Fast optical systems
The filter’s bandpass is designed for the incidence angles found in very fast optics, including f/2 Celestron RASA systems. Baader recommends this family for f/3.4 and faster optical systems. It is distinct from the standard slower-system narrowband filters and the narrower Ultra-Highspeed family.
Glass, cell and coatings
The filter uses 2 mm glass in a 5.5 mm ULP mounted cell. Reflex-Blocker hard coatings, plane-optical polishing, sealed coating edges and blackened edges are specified. The outer-rim indicator marks the telescope-facing side.
Imaging configuration
This is one filter, rather than an H-alpha/O-III/S-II set. The coating generation is optimised for CMOS cameras and is also suitable for CCD imaging. Use a holder that accepts the stated filter format and cell height.
Baader SII CMOS f/2 Highspeed 2" This 2-inch S-II filter is the 6.5 nm f/2 Highspeed version from Baader’s CMOS-optimised Precision Grade range. It isolates the S-II emission band for narrowband imaging, with the manufacturer’s wavelength reference at 671.7 nm.
Manufacturer model: Baader SII CMOS f/2 Highspeed 2" · Specifications checked against manufacturer data on 2026-11-04
