Two approaches to the deep sky.
The Optolong L-Quad Enhance + L-Para Filter Set pairs a versatile quad-band light-pollution filter with a 10nm Hα/OIII dual-band filter, giving color-camera astrophotographers a practical way to move between broadband deep-sky imaging and high-contrast emission-nebula imaging.
Why put these two filters together?
Because they solve different problems. The L-Quad Enhance preserves substantially more broadband color information for objects such as galaxies, star clusters, and reflection or mixed nebulae. The L-Para takes the opposite approach, isolating Hα and OIII emission to pull nebular structure away from the surrounding sky background.
Use either filter on its own, or capture data through both and combine the broadband color of the L-Quad with the narrowband structure of the L-Para during processing.
- Designed for color-camera astrophotography
- Useful for galaxies, nebulae, star clusters, reflection nebulae, and wide-field imaging
- More than 90% transmission at Hβ, OIII, Hα, and SII emission lines
- Suppresses common mercury and sodium light-pollution wavelengths
- Near-IR cutoff extending to 1000nm helps control unwanted IR
- Designed to retain more natural broadband color balance than narrowband filters
Conceptual wavelength guide only — not a measured transmission curve.
- 10nm FWHM bandpass centered on OIII at 500.7nm
- 10nm FWHM bandpass centered on Hα at 656.3nm
- More than 85% transmission of Hα and OIII in optical systems f/2 and slower
- Suppresses mercury, sodium, LED, and other unwanted light-pollution wavelengths
- Optimized for improved contrast and reduced halo behavior around bright stars
- Compatible with conventional telescopes as well as fast systems including RASA and HyperStar
Conceptual wavelength guide only — not a measured transmission curve.
Broadband color + narrowband structure
The real advantage of the L1 Dual-Combo Set is that you don't necessarily have to choose one filter or the other.
Which filter should I use?
A simple starting point for choosing between the two filters.
| Target | Start With | Why |
|---|---|---|
| Galaxies | L-Quad | Preserves broadband RGB and continuum signal |
| Star Clusters | L-Quad | Better suited to broadband stellar color |
| Reflection Nebulae | L-Quad | Reflection nebulae are broadband targets |
| Emission Nebulae | L-Para | Isolates Hα and OIII emission |
| Bright HII Regions | L-Para | Higher contrast for ionized gas structures |
| Mixed Broadband + Emission Targets | Use Both | Combine natural broadband color with narrowband detail |
Made for modern color-camera imaging
The L-Para is particularly useful for astrophotographers working with fast optical systems. Optolong specifies high Hα and OIII transmission for systems from f/2 and slower and specifically lists fast configurations such as RASA and HyperStar.
That makes the combination especially versatile for imagers who use one camera across multiple telescopes or regularly move between conventional refractors and faster astrographs.
Key specifications
Optolong coating technology
Both filters use multi-layer anti-reflection coatings and Optolong's ion-assisted deposition process. The coating system is designed for durability, scratch resistance, wavelength stability, and consistent transmission across the optical surface.
What's Included
- 1 × Optolong L-Quad Enhance 2" Filter
- 1 × Optolong L-Para 2" Filter
- Protective filter case / packaging