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
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.
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.
| 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) |
| Recommended focal ratio | f/4 and slower for this standard version |
Chroma 27009 SII 3nm · Chroma f/# performance data
Standard 27009, 36 mm unmounted; needs 36 mm unmounted filter wheel/holder.
| Target lines (nm) | 671.6; 673.1 |
|---|
Data sheet
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
