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.
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.
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.
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 manufacturer documentation
Exact manufacturer f/2 Highspeed 6.5 nm SKU matched by band and mounted size. Not the 3.5/4 nm Ultra-Highspeed model. Wavelength follows the exact manufacturer variant table, including S-II at 671.7 nm; no alternative line-centre value is silently substituted.
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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
