Chroma SII 3 nm 36 mm (27009) — ultra-narrowband, unmounted The Chroma 27009 SII 3 nm bandpass filter isolates the emission of singly ionised sulphur, a doublet at 671.6 nm and 673.1 nm common in nebulae, and separates it from the nearby H-alpha line at 656.3 nm. This 36 mm unmounted version suits filter wheels for APS-C and similar sensors.
Manufacturer model: Chroma 27009 SII 3nm, 36 mm unmounted · Specifications checked against manufacturer data on 2026-11-03
Chroma SII 3 nm 36 mm (27009) — ultra-narrowband, unmounted
The Chroma 27009 SII 3 nm bandpass filter isolates the emission of singly ionised sulphur, a doublet at 671.6 nm and 673.1 nm common in nebulae, and separates it from the nearby H-alpha line at 656.3 nm. This 36 mm unmounted version suits filter wheels for APS-C and similar sensors.
Chroma sputtered coatings
Made on a single high-grade glass substrate with hard sputtered coatings and no lamination, the filter withstands humidity and temperature extremes. The primary coating is on the front and an AR coating on the back to prevent ghosts. Chroma publishes measured spectral data for this filter collimated and at f/2.5 to f/5.
Specifications
Chroma part number
27009 SII 3nm Bandpass
Target lines
SII doublet, 671.6 nm and 673.1 nm
Bandwidth
3 nm
Format
36 mm diameter, unmounted
Coating
Hard sputtered; AR-coated back face
Substrate
Single glass substrate; 3 mm thick (Chroma astronomy brochure)
Chroma SII 3 nm 36 mm (27009) — ultra-narrowband, unmounted The Chroma 27009 SII 3 nm bandpass filter isolates the emission of singly ionised sulphur, a doublet at 671.6 nm and 673.1 nm common in nebulae, and separates it from the nearby H-alpha line at 656.3 nm. This 36 mm unmounted version suits filter wheels for APS-C and similar sensors.
Manufacturer model: Chroma 27009 SII 3nm, 36 mm unmounted · Specifications checked against manufacturer data on 2026-11-03
