How do light pollution filters work?

Light pollution filters reduce sky glow by only allowing particular wavelengths of light through them. Light emitted by street lamps, such as high-pressure sodium streetlights are rejected, allowing you to see more targets in the night sky. read more

Light-pollution reduction filters (henceforth, LPRFs) do work -- on some things. They are not a substitute for a clear sky, but they can and do provide improved views of many objects. Furthermore, filters can be of use even in very dark skies, not just ones that are significantly affected by city lights. read more

Unfortunately, light pollution has broadened in its coverage over the past few decades, so these filters tend to not work well visually under moderate to severe skyglow, although they can boost the contrast of some objects a little under a sky which is already fairly dark. read more