Optical glass lens; aluminum frame; significantly reduces light pollution; great for city and suburban observation UHC or light pollution reduction are designed to selectively reduce the transmission of certain wavelengths of light; especially those produced by artificial light Due to its ability to produce exceptionally for and clear images; this UHC filter is considered of the most popular astronomy accessories; it can be used not only for observations but also for astrophotography for Sky background is darker; and contrast of nebulae are noticeably; the perfect filter for viewing nebula from light polluted skies; or for boosting the contrast of nebula from dark for sky sites 1.25 ' ' diameter simply attach to eyepiece cased in a sturdy transparent for case; standard filter thread for 1.25 " eyepieces and other accessories, Manufacturer: Tsophreniq