The ZWO narrowband low-end filters are a first choice for astrophotographers - if they want to take the most contrasty CCD images at H-alpha, O-III or S-II wavelengths. The filters have excellent light transmission in the selected wavelength range, while at other "undesirable" wavelengths they cut off the light completely.
The filters are made of excellent glass material and machined for excellent contrast and sharpness. The coatings are applied to the glass material using state-of-the-art tools that guarantee an ideal transmission range. Anti-reflective coatings contribute to excellent imaging and the surfaces are treated to make the 2 mm glass material scratch-resistant.
Maximum light transmission of all three filters is above 80%, with the H-Alpha filter peaking at 656 nm, the O-III filter at 500 nm and the S-II filter at 672 nm, mainly helping to photographically capture nebulae, supernova remnants, etc. emitting in these wavelengths.