13% t moon filter, also known as neutral * filter (nd-0.9), is very suitable to help reduce glare and improve contrast, so that you can clearly see more functions of the moon, Venus and bright binaries, while reducing * *. This telescope filter is designed with high-quality neutral * optical glass and transmits only 13% of the light. It can not only reduce the brightness of the lunar surface, but also maintain the real color. Two side threads that can be screwed to most 1.25 inch eyepieces and other threaded accessories, such as Celestron, Orion, sky watcher, Meade, William, etc. In addition, you can stack with other filters for a lot of fun The 1.25 inch (about 3