Optolong L-Pro Light Pollution Telescope 2" Camera Filter

Optolong L-Pro Light Pollution Telescope 2" Camera Filter

The L-Pro filter is designed to improve the visibility of various deepsky objects. By selectively reducing the transmission of wavelengths of light pollutants, specifically those produced by artificial lights including mercury vapor lamps, both high and low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow). Together with the highly transparent in main nebula emission lines at OIII (496 nm and 500 nm), H-beta (486 nm), NII (654 nm and 658 nm), H-alpha (656 nm), as well as SII (672 nm), the filter is suitable for enhancing the contrast and details for both visual and photographic purpose at sub-rural area with heavy light pollution.

Unlike other light pollution filter UHC and CLS, L-Pro is multi-bandpass filter which offers better color balance by maximizing the transmission band. The balanced transmission allows astrophotos to be taken with minimal color cast to broadband emission objects such as galaxies, reflection nebulae and globular star clusters. L-Pro is the best choice for light pollution suppression.

Main Use and Performance

• Fits with CCD and DSLR cameras
• Works well on most emission nebulae, reflection nebulae and dark nebulae
• Suitable for visual observation and astrophotography
• L-Pro filter has a very low transmission reduction rate against continuous spectrum space objects, and thus is quite effective in suppressing light pollution sources when shooting galaxies, reflection nebulae and globular star clusters. The same holds true for visual star observations.
• L-Pro filter alone suppresses infrared wavelengths, and thus can be used at ease for “L” image shootings with CCDs
• Light pollution filters do not eliminate the effects of light pollution or increase the object’s brightness. In many cases, they increase the contrast between nebula and night sky, not brightening the nebula.
• Manufacturer's WARNING: The filters of Optolong are not designed for sun observation. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTER. You would be BLIND if you fail to observe the warning.

Image 1 (Left) shows The Orion Nebula after 1.9 hours of data with the L-Pro filter.

Image 2 (Center) shows The Orion Nebula after 180 seconds at ISO1600 with the L-Pro filter..

Image 3 (Right) shows The Orion Nebula after 180 seconds at ISO1600 with no filter. 

Technical Data

• Schott substrate material
• Thickness 2.0 mm (1.25-inch, 2-inch, and 77 mm)
• Thickness 1.0 mm (Clip series)
• Surface Quality: 60/40 (Refer to MIL-O-13830)
• Fine-optically polished to ensure accurate 1/4 wavefront and <30 seconds parallelism over the both surfaces
• High transmission at major nebula emission lines (i.e. H-alpha 656 nm; OIII 496 nm, and 500 nm; SII 672 nm; and H-beta 486 nm)
• Precision off-band blocking, specifically the major emission lines of artificial light pollution (i.e. Na 589 nm, Hg 435 nm and 578 nm)

Coating Parameter

• Multi-layers anti-reflection coating
• 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) no deviation affected by temperature change
• Planetary rotation system offers precision and homogeneity of coatings ensuring high value on transmission of pass-band and Optical density of off-band

Filter Cell

• Ultra-thin filter cell minimizes vignetting by maximizing possible clear aperture (clear aperture is 26 mm for 1.25-inch; 45 mm for 2-inch)
• Aerometal Material
• Precise CNC Machining
• Sand Blasting Process
• Black Anodized Finish
• Extinction Treatment to Prevent Reflection
• Laser Engraving for No Fading

• Use for most emission nebulae, reflection nebulae, and dark nebulae
• Suitable for both visual photographic observations
• Effective in suppressing light pollution sources