Features: The UHC telescope filter is designed to improve the images contrast of observed objects; It can be used not only for universe observations but for astrophotography 95%transmission of main nebulas emission lines and 0.1% transmission of offband specifically the majors emission lines of artificial light pollution; Great for city and suburban observation Double sided multi layer coating and the backside increases the broadbands penetration film reduces the reflecting light and increases the contrast and images sharpness Optical glass lens; Aluminum frame; Precise polish substrates good parallelism and precise ensures you used long time Including a plastic box convenient to carry and storage; Specifications: Material: Optical Glass Lens, Aluminum Frame Shape: Round UHC Filter Diameter:Approx.50mm/1.97in Thread:M48x0.75 Thickness:6.88mm Photo filter thread size: 2Inches Package Includes: 1xUHC Filter note: Please allow 1-2cm errors due to manual measurement,please make sure that you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item.