Optolong Oxygen III / O-III Narrowband (18nm) Nebula Filter - 1.25"
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A. About Optolong's O-III (18nm) FIlter
The Optolong O-III (Oxygen-III) filter is designed to improve the visibility of various deep sky objects. It does this by:
- Selectively reducing the transmission of wavelengths of light pollutants, specifically those produced by artificial lighting (including mercury vapor lamps, both high & low pressure sodium vapor lights, and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow)).
- Allowing 18nm bandwidth of light centered on a wavelength of 500nm to pass through, which corresponds to OIII emission lines.
This is a blue-green colored filter as OIII emits 495.9nm and 500.7nm. Many images of planetary nebulae and supernova remnants are taken only with H-alpha and OIII filters. They show great structural details, but have natural colors, looking like an RGB image.
B. Main Uses and Performance
- Suitable for visual observation on most emission nebulae, planetary nebulae and supernova remnants.
- Suitable for viewing on bright nebulae like M42 Orion Nebula under heavy light pollution.
- Use with a large aperture telescope under clear and dark viewing conditions with good seeing.
C. Spectral Curve Transmission Characteristics
- 90% transmission at major O-III lines at 495.9nm and 500.7nm.
- Precise and high blocking of major transmission lines of artificial light pollution:
- Hg (Mercury) at 435.8nm, 546.1nm, 577nm, and 578.1nm.
- Na (Sodium) at 598nm, 589.6nm, 615.4nm, and 616.1nm.
D. Technical Specifications
- Both surfaces are fine optically polished, accurate to 1/4 wavelength or better, and parallel to within 30 seconds or arc.
- 2mm thick Schott B270 optical glass substrate material.
- Very high surface quality of 60/40 or better (US Military Spec MIL-O-13830).
E. Optical Coating Specifications
- Multi layer anti-reflection coated.
- Non-cementing optical substrate coating.
- Electron-beam gun evaporation with Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL (central wavelength) so that there is no deviation due to temperature changes during use.
- Precise and homogeneous coatings ensure high values of desired passband and blocking of unwanted offband.
- Every single filter is tested and passed by Optolong before shipping to dealers.
F. Other
- 1.25" astronomy filter with standard M28.5x0.6 male filter thread (no female thread, so it cannot be stacked with other filters).
- Ultra-thin filter cell to minimize vignetting; clear optical aperture of 26mm.
- Precision CNC-machined metal filter cell with sand blasted black anodized finish, anti-reflection treatment, and laser engraving.
- High quality protective plastic storage case.
WARNING: Optolong filters are not designed for direct solar observation. NEVER use these filters for observing the Sun, or permanent eye and equipment damage will result.
Useful Resources
Filter Cell Specifications
D = Filter Cell Diameter = 31.3 mm / 1.23 in
T = Total Filter Height = 6.8 mm / 0.26 in
C = Filter Cell Height (Excluding Male Thread) = 4.8 mm / 0.18 in
M = Male Thread Length = 2.0 mm / 0.07 in
F = USABLE Female Filter Thread Length = Not threaded, so you cannot stack additional filters
S = Glass Substrate Thickness = 2 mm / 0.07 in
CA = Clear Aperture = 26.1 mm / 1.02 in
Other Information
- Country of Manufacture: China
A. About Optolong's O-III (18nm) FIlter
The Optolong O-III (Oxygen-III) filter is designed to improve the visibility of various deep sky objects. It does this by:
- Selectively reducing the transmission of wavelengths of light pollutants, specifically those produced by artificial lighting (including mercury vapor lamps, both high & low pressure sodium vapor lights, and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow)).
- Allowing 18nm bandwidth of light centered on a wavelength of 500nm to pass through, which corresponds to OIII emission lines.
This is a blue-green colored filter as OIII emits 495.9nm and 500.7nm. Many images of planetary nebulae and supernova remnants are taken only with H-alpha and OIII filters. They show great structural details, but have natural colors, looking like an RGB image.
B. Main Uses and Performance
- Suitable for visual observation on most emission nebulae, planetary nebulae and supernova remnants.
- Suitable for viewing on bright nebulae like M42 Orion Nebula under heavy light pollution.
- Use with a large aperture telescope under clear and dark viewing conditions with good seeing.
C. Spectral Curve Transmission Characteristics
- 90% transmission at major O-III lines at 495.9nm and 500.7nm.
- Precise and high blocking of major transmission lines of artificial light pollution:
- Hg (Mercury) at 435.8nm, 546.1nm, 577nm, and 578.1nm.
- Na (Sodium) at 598nm, 589.6nm, 615.4nm, and 616.1nm.
D. Technical Specifications
- Both surfaces are fine optically polished, accurate to 1/4 wavelength or better, and parallel to within 30 seconds or arc.
- 2mm thick Schott B270 optical glass substrate material.
- Very high surface quality of 60/40 or better (US Military Spec MIL-O-13830).
E. Optical Coating Specifications
- Multi layer anti-reflection coated.
- Non-cementing optical substrate coating.
- Electron-beam gun evaporation with Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL (central wavelength) so that there is no deviation due to temperature changes during use.
- Precise and homogeneous coatings ensure high values of desired passband and blocking of unwanted offband.
- Every single filter is tested and passed by Optolong before shipping to dealers.
F. Other
- 1.25" astronomy filter with standard M28.5x0.6 male filter thread (no female thread, so it cannot be stacked with other filters).
- Ultra-thin filter cell to minimize vignetting; clear optical aperture of 26mm.
- Precision CNC-machined metal filter cell with sand blasted black anodized finish, anti-reflection treatment, and laser engraving.
- High quality protective plastic storage case.
WARNING: Optolong filters are not designed for direct solar observation. NEVER use these filters for observing the Sun, or permanent eye and equipment damage will result.
A. About Optolong's O-III (18nm) FIlter
The Optolong O-III (Oxygen-III) filter is designed to improve the visibility of various deep sky objects. It does this by:
- Selectively reducing the transmission of wavelengths of light pollutants, specifically those produced by artificial lighting (including mercury vapor lamps, both high & low pressure sodium vapor lights, and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow)).
- Allowing 18nm bandwidth of light centered on a wavelength of 500nm to pass through, which corresponds to OIII emission lines.
This is a blue-green colored filter as OIII emits 495.9nm and 500.7nm. Many images of planetary nebulae and supernova remnants are taken only with H-alpha and OIII filters. They show great structural details, but have natural colors, looking like an RGB image.
B. Main Uses and Performance
- Suitable for visual observation on most emission nebulae, planetary nebulae and supernova remnants.
- Suitable for viewing on bright nebulae like M42 Orion Nebula under heavy light pollution.
- Use with a large aperture telescope under clear and dark viewing conditions with good seeing.
C. Spectral Curve Transmission Characteristics
- 90% transmission at major O-III lines at 495.9nm and 500.7nm.
- Precise and high blocking of major transmission lines of artificial light pollution:
- Hg (Mercury) at 435.8nm, 546.1nm, 577nm, and 578.1nm.
- Na (Sodium) at 598nm, 589.6nm, 615.4nm, and 616.1nm.
D. Technical Specifications
- Both surfaces are fine optically polished, accurate to 1/4 wavelength or better, and parallel to within 30 seconds or arc.
- 2mm thick Schott B270 optical glass substrate material.
- Very high surface quality of 60/40 or better (US Military Spec MIL-O-13830).
E. Optical Coating Specifications
- Multi layer anti-reflection coated.
- Non-cementing optical substrate coating.
- Electron-beam gun evaporation with Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL (central wavelength) so that there is no deviation due to temperature changes during use.
- Precise and homogeneous coatings ensure high values of desired passband and blocking of unwanted offband.
- Every single filter is tested and passed by Optolong before shipping to dealers.
F. Other
- 1.25" astronomy filter with standard M28.5x0.6 male filter thread (no female thread, so it cannot be stacked with other filters).
- Ultra-thin filter cell to minimize vignetting; clear optical aperture of 26mm.
- Precision CNC-machined metal filter cell with sand blasted black anodized finish, anti-reflection treatment, and laser engraving.
- High quality protective plastic storage case.
WARNING: Optolong filters are not designed for direct solar observation. NEVER use these filters for observing the Sun, or permanent eye and equipment damage will result.
Useful Resources
Filter Cell Specifications
D = Filter Cell Diameter = 31.3 mm / 1.23 in
T = Total Filter Height = 6.8 mm / 0.26 in
C = Filter Cell Height (Excluding Male Thread) = 4.8 mm / 0.18 in
M = Male Thread Length = 2.0 mm / 0.07 in
F = USABLE Female Filter Thread Length = Not threaded, so you cannot stack additional filters
S = Glass Substrate Thickness = 2 mm / 0.07 in
CA = Clear Aperture = 26.1 mm / 1.02 in
Other Information
- Country of Manufacture: China
Optolong Oxygen III / O-III Narrowband (18nm) Nebula Filter - 1.25"