The relentless spread of urbanization and its associated light pollution have become a growing problem for all amateurs and astrophotographers. The current fixes to the problem can be expensive and might include the purchase of a monochrome camera, several types of narrowband filters and a filter wheel.

The Astronomik CLS blocks the light of the spectral lines of mercury and sodium-vapor lamps and lets the largest part of the visible light and H-alpha emissions pass. All the important emission lines, as well as the spectral region that the very well dark adapted eye can see, can pass through the filter.