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3920 EUR
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price without VAT: 3187 EUR
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 Shop online:
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Shop in Warsaw (qty):
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Shop in Chorzow (qty):
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Artesky ERF 240 mm (SKU: ERF-240 ) is a high-class Energy Rejection Filter designed for safe use in H-alpha systems for solar observations. With a diameter of 240 mm and high optical quality, it effectively reflects heat and UV radiation, protecting optical elements from overheating and eliminating convection phenomena inside the telescope tube. The Artesky ERF filter is made of transparent optical glass with exceptionally high uniformity, polished to the class of lens surfaces. The dielectric layer is applied only on one side, which reduces stress and eliminates the risk of optical deformation. The filter transmits a 60nm band around the H-alpha line (656.28nm), effectively cutting off the entire remaining spectrum from 200 to 1100nm. The use of a filter at the front of the telescope stabilizes the internal temperature of the tube and minimizes air turbulence, which translates into a clearer, more contrasting image. With 95% transmission in the H-alpha band and OD4 attenuation, the filter works perfectly with H-alpha etalon filters (e.g. Daystar). Note: The Artesky ERF filter should only be used as a pre-filter in H-alpha solar observation systems. It should always be mounted in front of the telescope objective, with the reflective surface facing the Sun (marked with an arrow). Do not use the ERF filter alone for visual observations - it may cause permanent eye damage. Frameless version - if you need a version with a frame, please contact us or check other models in the solar filters category. • protects the H-alpha filter from overheating and damage
• eliminates air turbulence inside the tube, improving image sharpness
• reflects unwanted radiation bands (UV, IR, visible light except H-alpha) without absorbing heat
• ensures high light transmission in the H-alpha band – FWHM 60 nm
• made of high-quality optical glass with high uniformity and precisely controlled flatness
• dielectric coatings applied with the utmost care using advanced machines • ERF 240 mm reflective filter (without frame) • Optical diameter: 240 mm
• central wavelength: 656.28 nm (H-alpha)
• Transmission bandwidth (FWHM): 60 nm
• H-alpha band transmission: 95%
• reflection range: 200–1100 nm
• cut-off depth: OD4
• surface quality: λ/4, finish 60-40
• edge chipping: <0.2 mm
• glass thickness: 15 mm
• manufacturer: Artesky – Italy
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