Daystar Filters ERF 100 mm (glass + cell + 140 mm ID cap) – for refractor (SKU: E-140N100) is an Energy Rejection Filter designed for refractor telescopes used in hydrogen-alpha solar observation systems. Mounted at the front of the telescope, the filter reduces the amount of thermal energy reaching the H-alpha filter assembly by absorbing or reflecting ultraviolet and infrared radiation while transmitting the desired visible spectrum.

Key features

• Energy Rejection Filter designed for refractor telescopes
• reduces UV and IR radiation reaching the H-alpha filter assembly
• lowers thermal load on the optical system during solar observation
• improves operational stability of solar filters such as DayStar Quark and Quantum
• can also function as an aperture mask
• front-mounted installation on the telescope objective
• construction includes filter glass, mounting cell and protective cap

Box contents

• DayStar 100 mm ERF filter glass
• filter mounting cell
• 140 mm ID mounting cap

Technical specifications

• type: Energy Rejection Filter (ERF)
• filter diameter: 100 mm
• mounting cap inner diameter: 140 mm
• application: refractor telescopes
• mounting position: front of telescope objective
• compatibility: DayStar H-alpha solar observing systems

ERF filters are an essential component of solar observing setups because they reduce the heat reaching the H-alpha filter assembly, improving both operational safety and stability during solar observation and imaging.