Optolong UHC Light Pollution Filter
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Optolong UHC Light Pollution Filter

£43.00✓ 2 year warranty
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About this product

Model:  opt_uhc_1.25

Ultra High Contrast (UHC) Filter - Block Common Light Pollution Sources and Helps Increase the Visibility of Various Deep Sky Objects

The UHC (Ultra High Contrast) broadband filter is designed to improve the visibility of various deep sky objects. By selectively reducing the transmission of wavelengths of light pollutants, specifically those produced by artificial lightings including mercury vapour lamps, both high & low pressure sodium vapour lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow).

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 purposes at sub-rural area with heavy light pollution.

Warning - Optolong filters are not designed to be used for solar observation. Do not look at the sun through this filter as it will cause permanent eye damage.

FEATURES

  • 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)
  • Suitable for use with colour CCD and CMOS cameras and unmodified DSLRs
  • Narrower pass-band than CLS filter - Better suited for areas of higher light pollution 
  • UHC has a substantial red passband and offers superb views of objects like the Orion Nebula (M42)
  • 1.25" or 2" Mounted Sizes, EOS-C, EOS-FF and Nikon-FF Clip filters.
  • Supplied in a protective plastic case with EVA foam lining
  • 1mm (Clip Filters) or 2mm (1.25" / 2") Thick Schott Glass
  • Fine-optically polished on both sides - ensures accurate λ/4 wavefront and <30 seconds parallelism over the both surfaces

Transmission Chart

Red Line - Represents the transmission curve of the UHC Filter.

Green Line - The Major Emission Lines of Nebulae: H-α (656.3nm), H-β (486.1nm), OIII (495.9nm) and OIII (500.7nm)

Orange Line - The Major Emission Lines of Artificial Light Pollution: Hg / Mercury (435.8nm, 546.1nm, 577nm and 578.1nm), Na / Sodium (598nm, 589.6nm, 615.4nm and 616.1nm)

Technical Data

  • Schott substrate material
  • Thickness 2.0 mm (1.25”/2”)
  • 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
  • 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). Transmission of 0.1% is equivalent to OD3 (Optical Density), and a high optical density value indicates very low transmission, and low optical density indicates high transmission.

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 minimise vignetting by maximise possible clear aperture (clear aperture is 26mm for 1.25”; 45mm for 2”)
  • Aerometal Material | Precise CNC Machining | Sand Blasting Process | Black Anodised Finish | Extinction Treatment to Prevent Reflection | Laser Engraving No Fading

 

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