Optolong L-Para 2 inch 10nm Dual Narrow Band Filter

The Optolong L-Para (L-Parallels) is a next-generation dual narrowband 10nm light pollution filter engineered for astrophotographers who demand high efficiency, excellent contrast, and superior halo control across both fast and normal optical systems. Developed by Optolong, the L-Para is designed to extract stunning nebula detail even under severe light-polluted skies.

Featuring two perfectly balanced 10nm passbands, the L-Para isolates the most important nebular emission lines:

• OIII at 500.7nm

• H-Alpha at 656.3nm

In optical systems with focal ratios of F/2 and above, the transmission of both OIII and H-alpha exceeds 85%, ensuring high signal efficiency, darker backgrounds, and vivid nebular colors.

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Why a Dual 10nm Design? – The L-Para Philosophy

In Chinese culture, the number 10 symbolizes completeness and perfection. Inspired by the idiom “shi quan shi mei” meaning perfect in every way, Optolong designed the L-Para with dual 10nm bands—a representation of double excellence in performance and imaging experience.

This carefully chosen bandwidth strikes the ideal balance between light pollution suppression and signal strength, allowing photographers to achieve cleaner data without sacrificing exposure efficiency.

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Outstanding Performance Under Light Pollution

The Optolong L-Para effectively suppresses common artificial light pollution sources, including:

• Mercury vapor lamps

• High & low pressure sodium lamps

• Modern LED street lighting

By deeply blocking these unwanted wavelengths, while maintaining high transmission of nebula emissions, images captured with the L-Para show:

• Dark, neutral backgrounds

• High color accuracy

• Excellent contrast separation

• Rich nebula structure

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Excellent Anti-Halo Characteristics

Star halos are often caused by complex interactions within the optical system. While no filter can claim zero halos, the L-Para has undergone multiple rounds of optical design optimization and extensive testing, resulting in a significant reduction of halos around bright stars.

The result is cleaner star profiles and more professional-looking deep-sky images, even in demanding wide-field setups.

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Optimized for Fast & Normal Optics – One Filter for All Telescopes

Unlike many narrowband filters that struggle with fast systems, the Optolong L-Para is fully compatible with focal ratios from F/2 and above, including:

• Ultra-fast optics (RASA, HyperStar)

• Fast Newtonians

• Standard refractors and SCTs

Even when light strikes the filter at steep, oblique angles, the L-Para maintains high transmission and spectral stability, making it a truly universal dual-band filter.

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