Check the listing for details. SVBONY 1.25" CLS Deep Sky Filters contrast Increase between nebula and night sky. Condition: New. Listed at 33.29 USD. Product Description The SVBONY City Light Suppression broadband filter is designed to improve the visibility of various Deepsky objects. By selectively reducing the transmission of wavelengths of light pollutants, specifically those produced by artificial lightings including mercury vapor lamps, both high & low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow). Together with the highly transparent in main nebula emission lines at OIII(496nm and 500nm), H-beta (486nm), NII(654nm and 658nm), H-alpha(656nm) as well as SII(672nm), the filter is suitable for enhancing the contrast and details for both visual and photographic purpose at sub-rural area. Features: Multi-layers anti-reflection coating Non-cementing optical substrate coating Electron-beam gun evaporation with Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL (central wavelength) no deviation affected by temperature change. Planetary rotation system offers precision and homogeneity of coatings ensuring high value on transmission of pass-band and Optical density of off-band. Ultra-thin filter cell minimize vignetting by maximize possible Aerometal Material Precise CNC Machining Sand Blasting Process Black Anodized Finish Extinction Treatment to Prevent Reflection Laser Engraving No Fading 90% transmission of main nebula emission lines (i.e. Ha 656nm, OIII 496nm&500nm, SII672nm and H-beta 486nm). 0.1% transmission of off-band, specifically the major emission lines of artificial light pollution (i.e. Na 589nm, Hg 435nmand 578nm). Suitable for color CCD cameras and unmodified DSLRs CLS with wider pass-band than UHC and hence is more favored when observing under mild to moderate light pollution. Light pollution filter do not eliminate the effects of light pollution or increase the object ' s brightness. In many cases, they increase the contrast between nebula and night sky, not brightening the nebula. WARNING: The filters of SVBONY are not designed for sun observation. DO NOT LOOK AT THE SUN WITH SVBONY FILTER. You would be BLIND if you fail to observe the warning. Specifications: Brand: SVBONY Type: City Light Suppression Filter (CLS Filter) Material: Optical glass lens, Aluminum Frame Shape: Round Barrel diameter: 1.25'' Thread: Standard M28.5*0.6mm Net Weight: 5.2g / 0.18oz Package Includes SVBONY 1.25 inch CLS Filter Sturdy Plastic Case about svbony