Orion 5654 1.25-Inch UltraBlock NarrowBand Filter In areas plagued with significant light pollution, our UltraBlock eyepiece filter greatly increases contrast of emission and planetary nebulas Allows you to see features and details through a telescope that would normally be lost due to light pollution Blocks all forms of light pollution while passing critical hydrogen-beta and ionized oxygen wavelengths of light Enhances the sky presence of a significant number of fainter deep-sky objects Use with any filter-thread equipped 1.25" Orion eyepiece. Metal filter cell construction.