Optolong SII 3nm CCD 2" Filter

The Optolong SII 3nm CCD Filter (2") is a premium extra-narrowband filter designed for capturing faint sulfur II emission lines in nebulae. With an ultra-selective 3nm bandwidth centered at 672nm, this filter significantly suppresses background noise, allowing deep-sky imagers to extract subtle structural details with unmatched clarity.

Ideal for monochrome CCD or CMOS cameras, the SII 3nm filter works seamlessly with H-Alpha and OIII filters to compose Hubble-style false color images. It effectively blocks light pollution and skyglow, including emissions from mercury vapor and sodium vapor lighting, and cuts infrared wavelengths from 700nm to 1100nm—eliminating the need for a separate IR-blocking filter.

Manufactured using Optolong’s precision planetary rotation coating system and ion-assisted deposition, the SII 3nm delivers consistent transmission across the passband while maintaining optical stability under changing temperatures. The 2" filter cell is CNC-machined from aerospace-grade anodized metal and offers a full 45mm clear aperture for uncompromised imaging performance.

• Filter Type: Extra Narrowband – SII
• Center Wavelength: 672nm
• Bandwidth (FWHM): 3nm
• Transmission: High at SII emission line
• Infrared Block: 700–1100nm
• Off-band Rejection: <0.1% at Hg (435nm, 578nm) and Na (589nm)
• Filter Size: 2" (50.8mm)
• Clear Aperture: 45mm
• Substrate: Schott B260 Optical Glass
• Glass Thickness: 2.0mm
• Surface Quality: 60/40 (per MIL-O-13830)
• Wavefront Accuracy: λ/4
• Parallelism: <30 arcseconds
• Coating Method: Electron-beam with Ion-Assisted Deposition
• Filter Cell: CNC-Machined, Sandblasted, Black Anodized Aluminum
• Certifications: RoHS, TUV Rheinland, Bureau Veritas

• Optolong SII 3nm CCD 2" Filter
• Plastic Filter Case with EVA Foam Lining