Celestron's Moon Filter is an economical eyepiece filter for reducing the brightness of the moon and improving contrast, so greater detail can be observed on the lunar surface. The clear aperture is 21mm and the transmission is about 18%. Screws on to the filter thread of any Celestron, or other manufacturer's 1.25 inch eyepiece.
Celestron Moon Filter is ideal for astrophotographers looking to reduce light pollution and enhance detailed views of the Moon.