Celestron OptiView LPR binoculars have built-in light pollution reduction (LPR) filters designed to selectively reduce the transmission of certain wavelengths of light, specifically those produced by artificial light. This includes mercury, and both high and low pressure sodium vapor lights common in most city street lights. In addition, they block unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. sky glow). As a result, OptiView LPR binoculars darken the background sky, making deep-sky observation of nebulae, star clusters and even galaxies possible from urban areas.