Optolong L-Para filter 2" The L-Para is a dual 10 nm narrowband filter for OIII (500.7 nm) and H-alpha (656.3 nm). It keeps transmission above 85% at both lines in systems as fast as f/2, so it suits RASA and HyperStar systems as well as normal telescopes, and blocks mercury, sodium and LED lighting. Optolong rates it for Bortle 1–7 skies.
Manufacturer model: Optolong L-Para 2" · Specifications checked against manufacturer data on 2026-11-03
The L-Para is a dual 10 nm narrowband filter for OIII (500.7 nm) and H-alpha (656.3 nm). It keeps transmission above 85% at both lines in systems as fast as f/2, so it suits RASA and HyperStar systems as well as normal telescopes, and blocks mercury, sodium and LED lighting. Optolong rates it for Bortle 1–7 skies.
| Format | 2" mounted |
|---|---|
| FWHM | OIII 10 nm; H-alpha 10 nm |
| Centre wavelengths | 500.7 nm; 656.3 nm |
| Transmission | >85% at f/2 and slower |
| Suitable optics | f/2, f/2.8, f/3.2, f/4 and normal focal ratios |
| Blocks | Mercury, sodium and LED lines |
| Recommended skies | Bortle 1–7 |
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-Para 2" mounted.
| Centre wavelengths | 500.7 nm; 656.3 nm |
|---|---|
| Suitable optics | f/2, f/2.8, f/3.2, f/4 and normal focal ratios |
| Blocks | Mercury, sodium and LED lines |
| Recommended skies | Bortle 1–7 |
Data sheet
Optolong L-Para filter 2" The L-Para is a dual 10 nm narrowband filter for OIII (500.7 nm) and H-alpha (656.3 nm). It keeps transmission above 85% at both lines in systems as fast as f/2, so it suits RASA and HyperStar systems as well as normal telescopes, and blocks mercury, sodium and LED lighting. Optolong rates it for Bortle 1–7 skies.
Manufacturer model: Optolong L-Para 2" · Specifications checked against manufacturer data on 2026-11-03
