31.8mm UHC Filter Optolong

31.8mm UHC Filter Optolong

UHC (Ultra High Contrast) Filter is among the most popular filter types for reducing light pollution.

UHC filter is usually used for visual observation, it features the classic Gaussian cut which allows to redue light pollution coming from sodium lamps.

Utilization and Performance

Suitable for viewing low emission nebulae in H-beta 486nm, OIII 496nm, OIII 500nm, H-alpha 656nm, and SII 672nm with a transmission of 95% even in moon light or heavy light pollution conditions.

The UHC filter does not eliminate the effects of light pollution and does not increase the brightness of the object being shot, but instead increases the contrast between the nebula and the night sky, making image processing easier.

This UHC filter is designed to be attached to eyepieces, to filter wheels,  to filter drawers or directly on CLIP model cameras.

Techincal Specifications

Technical Data

• Schott substrate material
• Thickness 2.0 mm (1.25”/2”)
• Thickness 1.0 mm (Clip series)

Spectral Curve

• The Major Emission Lines of Nebulae
• H-b is 486.1 nm
• OIII is 495.9 nm and 500.7 nm
• SII is 672 nm
• H-a is 656.3 nm

• The Major Emission Lines of Artificial Light Pollution
• Hg is 435.8 nm, 546.1 nm, 577 nm, and 578.1 nm
• Na is 598 nm, 589.6 nm, 615.4 nm, and 616.1 nm

Coating Parameter

• Non-cementing optical substrate coating
• Electron-beam gun evaporation with low 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 tansmission of pass-band and Optical density of off-band