Optolong L-Para Dual Band Light Polution Filter - 2"

The Optolong L-Para is a brand new dual narrowband 10nm light pollution filter. The FWHM of L-Para is 10nm for OIII (500.7nm) and H-Alpha (656.3nm) respectively. The transmittance of nebulae emission lines at are both greater than 85% in systems with focal ratios of F2 and above. It effectively filters out mercury lamp, sodium lamp, and LED light pollution emission lines. At the same time, it has excellent contrast and anti-halo characteristics, allowing you to capture detailed and vivid images of nebulae. Optolong L-Para is suitable for both normal optical systems and very fast optical systems such as RASA and Hyperstar systems. Even when light is incident at an oblique angle, it can still maintain high transmission rates to provide you with a clear and precise shooting experience.

Ideal for astrophotography

The Optolong L-Para filter is the perfect choice for amateur astronomers who want to achieve maximum performance even under polluted skies. Its specific advanced optics make it a precious ally to capture every detail of the emission nebulae, with vivid colors and impeccable contrast.

Advantages

• Broad Compatibility: A dual narrowband filter suitable for all telescope systems, adaptable to fast optics (focal ratios of F2, F2.8, F3.2, F4) as well as various standard/normal focal ratio telescopes.
• Light Pollution Resistance: Effectively cuts off emission lines from mercury lamps, sodium lamps, LEDs, and other light pollution sources, making it applicable to Bortle Scale1- 9 dark skies.
• High Transmission Rate: In systems with a focal ratio of F2 and above, the transmittance of nebulae mission lines OIII and Ha exceed 85%, resulting in higher imaging efficiency.
• Excellent Contrast: The high transmittance of nebula emission lines (OIII & Ha) combined with deep cut-off of light pollution bands significantly improves image contrast and detail richness.
• Anti-Halo Characteristics: The design has undergone several round of optimizations and many times of repeated testing, resulting in a marked improvement in anti-halo performance, enhancing the capture of bright stars.

Specifications

• Bandwidth: 10nm (+/-0.5nm) for both Ha and OIII wavelengths, to maximize the definition of nebulae
• Optical material: Made with Schott monolithic optical substrate (not glued) for superior quality
• Glass thickness: 1.85 mm
• Surface quality: 60/40, compliant with US military standards MIL-O-13830
• Parallelism: 30", ensuring distortion-free images
• Transmission of the bandwidth: >85% @ 500.7nm & 656.3nm
• Blocking range: 300-1000nm
• Blocking: OD ave>4
• Optical coating: Entirely multi-coated, to reduce reflections and improve light transmission
• Optical flatness: Accuracy of 1/4λ (wave fronts) for optimal sharpness
• Filter Size: 2.0" (M48×0.75)