Optolong L-eXtreme filter 2" The L-eXtreme is a dual 7 nm narrowband filter isolating H-alpha and OIII for colour and monochrome cameras. With no passband between H-beta and OIII it admits less light pollution than the L-eNhance, for darker skies in images and stronger nebula contrast.
Manufacturer model: Optolong L-eXtreme 2" · Specifications checked against manufacturer data on 2026-11-03
The L-eXtreme is a dual 7 nm narrowband filter isolating H-alpha and OIII for colour and monochrome cameras. With no passband between H-beta and OIII it admits less light pollution than the L-eNhance, for darker skies in images and stronger nebula contrast.
Specifications
Format
2" mounted
FWHM
OIII 7 nm; H-alpha 7 nm
Substrate
B270
Thickness
1.85 mm
Peak transmission
>90%
Blocking range
300–1000 nm
Light-pollution line blocking
>99%
Surface quality
60/40
Transmitted wavefront
λ/4 RMS
Parallelism
30"
Coating
Multi-layer anti-reflection coating on a non-cemented substrate, applied by ion-assisted deposition for durability and a stable centre wavelength with temperature.
Optolong L-eXtreme filter 2" The L-eXtreme is a dual 7 nm narrowband filter isolating H-alpha and OIII for colour and monochrome cameras. With no passband between H-beta and OIII it admits less light pollution than the L-eNhance, for darker skies in images and stronger nebula contrast.
Manufacturer model: Optolong L-eXtreme 2" · Specifications checked against manufacturer data on 2026-11-03
