Chroma OIII 3nm Ultra filter - 2″ mounted

3nm OIII filter from Chroma Technology

Visit 3nm OIII filter from Chroma Technology is an ultra-narrow band filter designed for astronomical imaging. It is optimized to capture the emission line of doubly ionized oxygen (OIII) at 500.7 nm, revealing the detailed structures of planetary and diffuse nebulae. This filter is ideal for astrophotographers seeking maximum contrast and effective suppression of unwanted wavelengths.

Key features

• Bandwidth : 3 nm, offering extremely precise isolation of the OIII line while blocking parasitic emissions (sodium lamps, mercury, etc.).
• High transmission : Up to 90 % at 500.7 nm, guaranteeing optimum signal-to-noise ratio.
• Optical quality :
  • Surface polished to an accuracy of λ/4.
  • Multi-layer anti-reflective coatings on both sides to minimize halos and stray reflections.
• Available formats :
  • Mounted: 1.25", 2".
  • Unmounted: 31 mm, 36 mm
• Substrate thickness : Approx. 3 mm, made from a single optical glass substrate for exceptional durability.

Applications

• Imaging OIII-rich nebulae :
  • Ideal for capturing celestial objects such as the Orion Nebula, the Rosetta Nebula and the Veil Nebula.
• Reducing light pollution :
  • Effectively blocks unwanted wavelengths, even in urban or suburban environments.
• Advanced astrophotography :
  • The perfect complement to H-alpha and SII filters for producing images in scientific palettes (SHO or Hubble palette).
• Compatibility with high-speed systems :
  • Works perfectly with focal ratios up to f/4.0.
  • An optimized version is available for high-speed systems (f/2.6 to f/3.6) 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 : Fits most filter wheels and drawers on the market.

Conclusion

The filter Chroma OIII 3nm is a high-performance tool for deep-sky imaging. Its optical precision, high transmission and ability to effectively reduce light pollution make it an essential choice for both amateur and professional astrophotographers seeking to capture the subtle details of nebulae rich in ionized oxygen (OIII).