This useful telescope eyepiece filter transmits 25% of incoming light. It's ideal for viewing crescent Moon phases and for smaller-aperture telescopes, for which less dimming is required.When the Moon is in its crescent phase, it does not produce as much glare as when it is full or waxing, but filtration is still recommended to achieve optimal view quality. When looking at the Moon in relatively small (60mm-80mm) telescopes, the brightness is not as distracting as in larger telescopes, but some filtration is required to get the best observations. To improve contrast and tone down glare easily in these situations, we recommend using a neutral-density 1.25" Orion 25% Transmission Moon Filter. This inexpensive accessory threads directly into a 1.25" eyepiece barrel and blocks 75% of the light gathered by the telescope. Once installed on a 1.25" telescope eyepiece, the Orion 25% Transmission Moon Filter will bring out considerably more lunar surface details thanks to the boosted contrast. Not only will more surface features and details pop out, but you can study them in greater comfort, thanks to Moon Filter reducing overall brightness without altering color. This neutral-density telescope eyepiece filter reduces irradiation, which is the distortion at the boundary between light and dark areas, such as along the lunar terminator. Using a Moon filter also helps conserve dark-adapted vision while viewing the lunar surface.