Baader 7.5 nm Solar Continuum 2" Filter, ZWL 540 nm with 2" screw thread. A must-have for refractor owners: These telescopes narrow down the spectral range where lens optics perform with the sharpest and most contrast. The Baader Solar Continuum Filter enhances performance, increases contrast, and blocks atmospheric turbulence (when used in combination with white light solar filters). It provides a significant contrast gain in monochrome photography, even with color-accurate systems. Important note: The Baader Solar Continuum Filter should only be used for visual solar observation with additional filtering (e.g., Herschel prism or AstroSolar solar filter film).