Reject Filter ERF 200mm with Metal Cell Artesky (SKU: ERF-200-MC248) all astro filters opinie

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Artesky ERF 200mm in metal frame (SKU: ERF-200-MC248 ) is a high-class Energy Rejection Filter designed for safe use in H-alpha solar observation systems. By mounting at the front of the telescope, it effectively reflects most of the solar energy, preventing overheating of the standard and eliminating convection phenomena inside the tube. This filter does not absorb heat, but reflects it, remaining cool during operation and maintaining the internal temperature of the telescope close to the ambient.

Unlike absorbing filters, the Artesky ERF filter is made of optical glass with very high homogeneity and a precisely polished surface, with a dielectric coating applied only on one side. This solution eliminates stresses that can lead to surface deformation and image quality deterioration. The transmission range has been precisely limited to a band of 60 nm around the H-alpha line (656.28 nm), with effective reflection of radiation from the range of 200-1100 nm.

The coatings are applied using the most advanced optical coating technology, ensuring geometric stability and maintaining the full resolving power of the telescope. The filter drastically reduces the thermal energy entering the optical system, improving image contrast and minimizing interference caused by heating. Due to its high transmission in the H-alpha band (95%) and the depth of attenuation of OD4, the filter is perfect as a pre-filter for systems with Daystar or similar filters.

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 layer facing the Sun (marked with an arrow on the mount). Do not use the ERF filter alone for visual observations - this can cause permanent eye damage.

Why use an ERF filter?

• 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

Set components

• ERF 200 mm reflective filter in a metal frame

Technical parameters

• optical diameter: 200 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: 12 mm
• frame: aluminum 6061, anodized
• frame thickness: 4 mm
• inner diameter of the frame: 248 mm
• Outer diameter of the housing: 256 mm
• manufacturer: Artesky – Italy