Chroma SII filter 8nm - 2″ mounted

8nm SII filter from Chroma Technology

Visit 8nm SII filter from Chroma Technology is a narrow-band filter designed to isolate the ionized sulfur emission line (SII) at 672 nm. It is ideal for imaging sulfur-rich nebulae, capturing spectacular detail in deep-sky objects while reducing light interference.

Key features

• Bandwidth : 8 nm, providing effective isolation of the SII line while blocking unwanted wavelengths, such as those from light pollution or sodium and mercury lamps.
• High transmission : Up to 94 % at 672 nm, guaranteeing an excellent signal-to-noise ratio for capturing the subtle details of nebulae.
• Targeted emission rays : SII doublet at 671.6 nm and 673.1 nm, characteristic of sulfur-rich regions.
• Optical quality : Surface polished to an accuracy of λ/4.
• Multi-layer anti-reflective coatings : To minimize halos and stray reflections.
• Available formats :
  • Mounted: 1.25", 2".
  • Unmounted: Customized formats (31 mm, 36 mm).
• Substrate thickness : Approx. 3 mm, guaranteeing exceptional durability.

Applications

• Imaging SII-rich nebulae:
  • Ideal for capturing objects such as the Crab Nebula, Rosette Nebula and Veil Nebula.
• Reducing light pollution :
  • Effectively blocks unwanted wavelengths, even in urban environments or under polluted skies.
• Advanced astrophotography :
  • The perfect complement to H-alpha and OIII filters for scientific palette images (SHO or Hubble palette).
• Compatibility with high-speed systems :
  • Works perfectly with focal ratios up to f/4.0.
  • Can be used successfully on very fast systems (f/2.8 to f/3.6), although an optimized version is recommended to compensate for blueshift.

Technical highlights

• Exceptional durability :
  • Sputter coatings guarantee long-term spectral stability.
  • Resistant to extreme variations in temperature and humidity.
• Anti-halos design : Anti-reflective coatings eliminate halos around bright stars, delivering sharp, detailed images.
• Universal compatibility : Compatible with most filter wheels and drawers on the market.

Conclusion

The filter Chroma SII 8nm is an essential tool for deep-sky imaging. Its bandwidth is slightly wider than that of ultra-narrow filters (3 or 5 nm), enabling it to capture more signal while offering excellent contrast. It is an essential choice for astrophotographers wishing to reveal the subtle details of nebulae rich in ionized sulfur (SII).