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.
Specifications
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
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-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
