The Svbony SV115 OIII Filter (2") is an excellent choice for amateur astronomers looking to minimize the effects of light pollution, thanks to its affordable price and good quality.
How does an OIII filter work?
The filter works through selective light transmission. The glowing gases in emission nebulae (such as the Orion Nebula or the Veil Nebula) do not radiate across the entire visible spectrum; instead, they emit light 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 and transmits light only within a narrow band. It filters out light from mercury and sodium vapour lamps used for street lighting, as well as natural atmospheric glow (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 is significantly increased against the darker sky background.
Recommended for telescopes with larger (20 cm) apertures.
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)
- Light 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