Optolong OIII CCD 6.5nm 1.25" Mounted Filter

The Optolong OIII CCD 6.5nm Filter (1.25") is an advanced narrowband filter designed to isolate the oxygen-III emission line at 500nm, a critical wavelength for revealing intricate structures in emission and planetary nebulae. Its 6.5nm bandwidth dramatically improves contrast by rejecting artificial light and atmospheric skyglow, making it ideal for imaging in both dark and light-polluted environments.

This filter enhances the blue-green oxygen signature while suppressing stars and unwanted background, allowing astrophotographers to extract rich structural detail in nebulae and supernova remnants. Used alone or alongside H-alpha and SII filters, it supports tri-color (SHO) Hubble-style image composition.

Manufactured with Schott B260 optical glass and multi-coated using electron-beam evaporation with ion-assisted deposition, the OIII filter ensures central wavelength stability, high durability, and minimal light scatter. The CNC-machined 1.25" cell provides a 26mm clear aperture, precision construction, and long-lasting performance under rigorous imaging conditions.

• Filter Type: Narrowband – OIII (Oxygen-III)
• Center Wavelength: 500nm
• Bandwidth (FWHM): 6.5nm
• Transmission: ~80% at 500nm
• Infrared Block: 700–1100nm
• Off-band Rejection: <0.1% at Hg (435nm, 578nm), Na (589nm)
• Filter Size: 1.25" (31.75mm)
• Clear Aperture: 26mm
• Substrate: Schott B260 Optical Glass
• Glass Thickness: 2.0mm
• Surface Quality: 60/40 (MIL-O-13830)
• Wavefront Accuracy: λ/4
• Parallelism: <30 arcseconds
• Coating Method: Electron-Beam Evaporation with Ion-Assisted Deposition
• Filter Cell: CNC-Machined, Sandblasted, Black Anodized Aluminum
• Manufacturing System: Optolong Planetary Rotation Coating
• Certifications: RoHS, TUV Rheinland, Bureau Veritas

• Optolong 1.25" OIII CCD 6.5nm Filter
• Protective Filter Case with High-Pressure EVA Foam