ERF 150

The Artesky ERF 150 is a high-quality energy rejection filter (pre-filter) essential for H-alpha solar observation and imaging. It prevents excessive solar energy from reaching your telescope and H-alpha filter etalon by reflecting wavelengths from 300nm to 1100nm while transmitting only a 60nm spectral window centered on H-alpha (656.28nm), dramatically reducing thermal stress and optical distortion. The filter features a homogenous, transparent glass substrate with precision dielectric coatings applied on advanced optical coating machinery, preserving full telescope resolving power while minimizing heat buildup and air turbulence inside the telescope tube. Artesky ERF filters must be mounted in front of the telescope objective as a pre-filter to any H-alpha narrow-band filter system.