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.
| 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" |
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 2" mounted. Standard L-eXtreme, not L-eXtreme F2 (fast optics).
| Peak transmission | >90% |
|---|
Data sheet
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
