The city at night is colorful, brightly lit, and bustling with traffic, showcasing the prosperity of the city. Urbanization also brings new problems, as light pollution is ubiquitous in cities. For amateur astrophotographers, to capture a good astronomical work in the city, they need at least the following equipment: a black and white astronomical camera with cooling function, a filter wheel, and astronomical filters for single channel shooting with black and white cameras. They also need at least 3 pieces for color image synthesis. The SVBONY SV220 filter is a dual bandpass filter specifically designed for color CMOS, CCD, or digital cameras. The dual bandpass narrowband filter is a more cost-effective and portable solution for astronomical photography. Even in areas with bright full moons and severe light pollution, normal astronomical photography can still be conducted. The dual narrowband design is a technological innovation in the field of astronomical filters. The filter allows for high transparency of OIII (500.7nm) and H-Alpha (656.3nm) nebula emission lines while filtering out the majority of artificial light damage and the impact of sky light.   1. No need to travel mountains or water, you can enjoy deep space photography anytime and anywhere in the city: With the help of dual narrow filters, customers can take deep space photography in areas with severe light damage (full moon state+8level light damage area).   3.Double narrow filters can achieve capturing large fullcolor images with a single exposure. 4. 7nm ultra narrowband flux+OD5 cutoff depth+average peak transmittance of over 90%, ensuring that the astronomical materials captured are sufficiently pure and not affected by non target spectral interference. Precautions: 1. Dual narrowband filters are not suitable for short focal ratio telescopes, such as Stellar RASA (f/2); In short focal ratio shooting systems, there will be a significant shift in the center wavelength. Various tests have shown that this type of dual narrowband filter is more suitable for shooting on main lenses with focal ratios of f/5 and above.   2. Not suitable for broadband themed photography targets; For example, galaxies, reflection nebulae, etc 3. Suitable for shooting in areas with extreme light damage level 8 and below, as areas with higher light damage levels may cause some problems 4. The filter will have a certain amount of glow, color cast, and halo in the OIII (500.7nm) channel, which is the normal performance of this level of filter.   specifications parameter Product specifications 2 inches Mirror ring size Φ50.8x10mm weight 15-20g Thread type Single thread/male thread Thread specifications M48*0.75 material quality 6061T aluminum profile   CNC/Blackening Extinction Oxidation base material Corning EAGLE substrate thickness 1.80+0.07/-0.03mm clear aperture 44mm FWHM (Half peak transmittance) 500.7nm±1nm-7nm±2nm 656.3nm±1nm-7nm±2nm Cut off wavelength 300-1000nm Cut off depth OD5 Peak transmittance 94% surface quality 60/40 Surface parallelism λ/2 Package List: SVBONY 2 "7nm filter PP material rubber box