Optolong 1.25 UHC Filter
The UHC filter cancels out the brightness of the sky background caused by artificial light. On the contrary, if they let pass the wavelengths emitted preferentially by celestial objects similar to fog.
The effect to the viewer is a significant increase in contrast. The use of the UHC filter is not only used in the case of light pollution. Contrast also enhances low dark skies.