The bright moonshine is filtered so that structures are more visible. The filter is simply screwed into the socket of the eyepiece or a camera. The filter effect is not achieved in this moon filter by colored glass. It is rather a so-called neutral density filter. Neutral density filters (gray filters) are ideal for all situations in which overshoot is to be prevented and the object should not appear colored. The classic application is the lunar observation. Also for the additional attenuation during the solar observation these filters are very well suited, however they do not replace the actual sun filter!