Optolong L-Pro Light Pollution Telescope 1.25″ Camera Filter

The Optolong L-Pro filter (1.25-inch version) 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 (496nm and 500nm), H-beta (486nm), NII (654nm and 658nm), H-alpha (656nm), as well as SII (672nm), 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.

Compare the L-Pro, L-eXtreme, and L-eNhance filter transmission lines:

Click on the Gallery tab thumbnail images to see the transmission lines in greater detail.

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

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 26mm for 1.25-inch; 45mm for 2-inch)
• Aerometal Material
• Precise CNC Machining
• Sand Blasting Process
• Black Anodized Finish
• Extinction Treatment to Prevent Reflection
• Laser Engraving for No Fading

• Optolong L-Pro filter is perfect for astrophotographers fighting light pollution
• Best used for imaging most emission nebulae, reflection nebulae, and dark nebulae
• Suitable for both visual photographic observations
• Effective in suppressing light pollution sources