Filter Chroma S-II 3 nm 65x65 mm, unmounted (SKU: CT-27009-65X65) all astro filters opinie

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The Chroma S-II 3 nm 65x65 mm Unmounted (SKU: CT-27009-65X65) is a large square format narrowband filter designed for the most demanding astrophotography systems. With its ultra-narrow 3 nm bandwidth, it precisely isolates the S-II sulfur line at 672.4 nm, enabling high-contrast, high-detail images, even in light-polluted conditions.

Key features

• 3 nm bandwidth tuned to the S-II line (approx. 672.4 nm)
• bandwidth transmission at approximately 99%
• hard coatings applied using the reactive magnetron sputtering method – exceptional durability and stability of optical parameters
• anti-reflective coatings on the back surface eliminate reflections and ghosting
• all Chroma Astronomy filters are parfocal to each other
• optimized for use in f/4 and slower optical systems, the 3nm version also performs well at f/3
• the filter is not suitable for observing the Sun

Set components

• S-II filter 3 nm 65x65 mm unframed – CT-27009-65X65

Technical parameters

• type: S-II narrowband filter for astrophotography
• format: 65x65 mm, unframed
• bandwidth: 3 nm
• central wavelength (CWL): approx. 672.4 nm
• transmission: approx. 99%
• optical substrate: 3.0 mm thick glass
• coating technology: reactive magnetron sputtering (hard coatings)
• coating construction: main layer on the front side, AR coatings on the back side
• Transmitted wavefront accuracy: better than 0.25 waves/inch
• parfocal: yes (with other Chroma Astronomy filters)
• production: USA (Vermont)