Optolong UHC Light Pollution Filter for Urban Environment – 1.25″

Introduction The UHC (Ultra High Contrast) 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 photograghic purpose at sub-rural area with heavy light pollution. Main Use and Performance Suitable for color CCD cameras and unmodified DSLRs. UHC with narrower passband provides higher contrast than CLS. Thus it is more suitable for urban environment where you suffer from severe light pollution. UHC has a substantial red passband and offer superb views for objects like the Orion Nebula (M42). 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 Optolong are not designed for sun observation. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTER. You would be BLIND if you fail to observe the warning. Technical Data Sbustrate: optical glass Tave>95% Blocking range: 300-700nm Blocking depth: OD3, light pollution line blocking >99% Surface quality: 60/40 (Refer to MIL-O-13830A, MIL-C-48497A) Transmitted Wavefront RMS:  ¼ λ Parallelism: 30s UHC Spectrum and Characteristic How to read the chart? ▲The horizontal axis is the Wavelength in Nanometers(nm). ▲The vertical axis is transmission in %. ▲The RED line shows the line of H-alpha. Green line shows the emission of OIII. The artifcial emission lines are shown in ORANGE. Coating Technology Multi-layers anti-reflection coating Non-cementing optical substrate coating Optolong filter adopts precision coating based on 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. Optolong UHC Performance 1. The Milky Way Hongkong, Cityscape shot by Vincent Cheng 2. NGC2244 Rosette Nebula _by Dengyunwei Using Optolong UHC filter 3. You can see the Milky Way in Kunming City, image shot by Yule who used Optolong UHC. See the compare. 4. M42 by Jxsky, Optolong UHC filter 5. Compare image by astrophotographer Luocheng.