The Svbony SV115 OIII filter (1.25") offers excellent value and quality, making it an ideal choice for amateur astronomers looking to minimize the effects of light pollution.
How does an OIII filter work?
The filter works by selectively transmitting light. The glowing gases in emission nebulae, such as the Orion Nebula or the Veil Nebula, do not emit light across the entire visible spectrum; instead, they radiate at specific wavelengths. One of the most important of these emission lines is the OIII doublet of doubly ionized oxygen.
The filter blocks most of the visible spectrum, transmitting light only within a narrow band. It filters out light from mercury- and sodium-vapour lamps used for street lighting, as well as the natural glow of the atmosphere (airglow).
The Svbony SV115 OIII filter opens a narrow 18 nm-wide "window" (FWHM) around the 500 nm wavelength, where the OIII lines (495.9 nm and 500.7 nm) are located, transmitting them with 90% efficiency. As a result, emission nebulae do not become brighter, but their contrast increases significantly against the darker sky background.
Recommended for telescopes with an aperture of 20 cm or larger.
Features:
- Size: 2 inch (compatible with all standard 2" eyepieces and accessories)
- Bandwidth (FWHM): 18±2 nm (positioned between very narrow OIII and wider UHC filters)
- Transmission: 90% at the OIII peaks
- Construction: Aluminium alloy ring, high-quality optical glass with multilayered anti-reflective coatings
- Protection: Supplied in a foam-lined plastic protective case