Optolong L-eNhance Dual (Triband) Bandpass Imaging Filter - 2"

A. About Optolong's L-eNhance FIlter

The relentless spread of urbanization and its associated light pollution have become a growing problem for all amateurs and astro photographers. The current solutions to the problem can be expensive and might include the purchase of a monochrome camera, several types of narrowband filters and a filter wheel.

L-eNhance provides an economical and practical solution for amateurs. It is a dual-band pass filter which has been designed for DSLR (digital SLR), color CMOS and CCD cameras. The convenience and cost effectiveness of this filter allows amateurs to image a rich selection of astronomical images, even in bright, heavily light-polluted areas.

Optolong's L-eNhance filter effectively isolates the H-Alpha, H-Beta, and Oxygen III nebula emission lines and achieves a maximum transmission of around 90%. The performance of this filter delivers images that superbly control the impact from light polluted skies.

B. Spectral Curve Transmission Characteristics

According to the characteristics of celestial body emission lines and features of light pollution spectrum, Optolong specially designed and optimized dual-band L-eNhance filter characteristics in order to retain the prominent RGB colors of nebulae while blocking out most light pollution.

• Peak transmission: > 90%
• Blocking range: 300 - 1000nm
• Light pollution line blocking depth: > 99%

C. Technical Specifications

• Both surfaces are fine optically polished, accurate to 1/4 wavelength or better, and parallel to within 30 seconds or arc.
• 1.85mm thick Schott B270 optical glass substrate material.
• Very high surface quality of 60/40 or better (US Military Spec MIL-O-13830).

D. Optical Coating Specifications

• Multi layer anti-reflection coated.
• Non-cementing optical substrate coating.
• Electron-beam gun evaporation with Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL (central wavelength) so that there is no deviation due to temperature changes during use.
• Precise and homogeneous coatings ensure high values of desired passband and blocking of unwanted offband.
• Every single filter is tested and passed by Optolong before shipping to dealers.

E. Other

• 2" astronomy filter with standard M48x0.75 male filter thread (no female thread, so it cannot be stacked with other filters).
• Ultra-thin filter cell to minimize vignetting; clear optical aperture of 45mm.
• Precision CNC-machined metal filter cell with sand blasted black anodized finish, anti-reflection treatment, and laser engraving.
• High quality protective plastic storage case.

WARNING: Optolong filters are not designed for direct solar observation. NEVER use these filters for observing the Sun, or permanent eye and equipment damage will result.