Optolong L-Pro Filter 1.25" Mounted

The L-Pro filter from Optolong is a multi-bandpass filter that works well for visual use as well as photographic use with CCD cameras and DSLR’s. Better color balance is achieved by maximizing the transmission band, allowing you to produce images of broadband emission objects with nominal color cast. Use the L-Pro filter alone to suppress infrared wavelengths when doing photography, or as a light pollution suppression filter when observing visually.

By reducing the transmission of artificial and natural light pollution, including neutral oxygen (skyglow) as well as light given off from mercury and sodium vapor lamps, the background sky will become darker, allowing the good stuff to shine through. High transmission of main nebulae emission lines at OIII, H-Beta, NII, H-alpha, and SII, when combined with the precision off-band blocking of contrast-killing light pollution, makes the Optolong L-Pro filter perfect for most emission nebulae, reflection nebula, and dark nebulae.

The Optolong 1.25” L-Pro Filter is made with Schott glass that has been multi-coated with an ion-assisted deposition technology to ensure scratch resistance and stability on the central wavelength, or CWL. The filter cell is made of lightweight, strong metal and is CNC machined, sand-blasted, black anodized, and then laser engraved. The result is a super thin filter cell that will produce a clear aperture of 26mm.

Quality Filter Materials:

• Schott B260 substrate material from Germany, 2.0mm thick
• CNC machined and black anodized aero-metal filter cell that is ultra-thin to provide largest clear aperture; Laser-engraved to prevent fading
• Multiple layers of anti-reflection non-cementing coatings applied via electron-beam gun evaporation with Ion-assisted deposition

Optolong Filter Manufacturing Processes and Parameters

• Filter substrate is fine-optically polished to 1/4 wave and <30 parallelism over both surfaces
• Surface quality, according to MIL-O-13830, is 60/40
• 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)
• High value transmission of pass-band and optical density of off-band is assured through Optolong’s planetary rotation system, a homogenous and precise coating procedure
• Thin metal cells have a clear aperture of 26mm for 1.25” filters
• Each filter comes with a plastic case with high pressure EVA case lining