Optolong UHC Filter 1.25" Mounted - Light Pollution Reduction for Astrophotography - Perfect for Deep Sky Observation with Telescopes

Optolong's 1.25" Ultra High Contrast (UHC) will show you more defined contrast than your average CLS filters, however, it works much the same. This UHC filter virtually eliminates light pollution caused by both artificial and natural sources, delivering views of darker skies and increasing visibility of your favorite deep-sky objects. Skyglow, that is caused by neutral oxygen in the atmosphere and light from high and low-pressure sodium vapor lights and mercury vapor lamps, are suppressed significantly. This means that you can enjoy views or images from areas with heavy light pollution.

Optolong’s UHC filter lets desirable wavelengths pass at a peak transmission of 95%, including emission lines at OIII, H-Beta, NII, H-Alpha, and SII. This filter also has a substantial red passband, so objects like the Orion Nebula look awesome!

The Optolong 1.25” UHC 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. Each 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
• 95% transmission of main nebula emission lines (i.e. H-alpha 656nm, OIII 496nm and 500nm, SII 672nm and H-beta 486nm)
• 0.1% transmission of off-band, specifically the major emission lines of artificial light pollution (i.e. Na 589nm, Hg 435nm and 578nm)
• Optolong’s planetary rotation system is a homogenous and precise coating procedure that ensures both high transmission of pass-band and optical density of off-band
• Each filter comes with a plastic case with high pressure EVA case lining
• Thin metal cells have a clear aperture of 26mm for 1.25” filters

About Optolong

Optolong is the Astronomy Filters division of Yulong Optics, an optical filter design and processing company out of Kunming, China that has provided filters for over 700 optical companies since 1999. All Optolong filters pass European Union RoHS requirements and have been certified by TUV Rheinland and Bureau Veritas.