{"product_id":"optolong-filtro-sii-6-5nm-1-25-31-8mm-banda-stretta-672nm","title":"Optolong SII Filter 6.5nm 1.25\" – Narrowband 672nm","description":"\u003ch2\u003eOptolong SII Filter 6.5nm 1.25\" (31.8mm) for Narrowband Astrophotography\u003c\/h2\u003e\n\u003cp\u003eThe \u003cstrong\u003eOptolong SII 6.5nm 1.25\"\u003c\/strong\u003e is a \u003cstrong\u003enarrowband Sulfur II (672 nm) filter\u003c\/strong\u003e designed for deep-sky astrophotography with CCD and CMOS monochrome cameras. With a 6.5 nm bandwidth centered at 672 nm, it selectively isolates the SII emission line, significantly improving contrast on emission nebulae even under light-polluted or moonlit skies.\u003c\/p\u003e\n\n\u003ch2\u003eOptimized for SHO Imaging (H-alpha, OIII, SII)\u003c\/h2\u003e\n\u003cp\u003eThis SII filter is engineered for use in combination with \u003cstrong\u003eH-alpha and OIII filters\u003c\/strong\u003e in a \u003cstrong\u003eSHO narrowband setup\u003c\/strong\u003e, enabling tricolor imaging in the well-known Hubble palette style. Narrowband imaging with an SHO set can be performed even in urban environments, as the filter enhances the contrast between nebula and background sky.\u003c\/p\u003e\n\u003cp\u003eA narrowband filter does not increase object brightness but improves signal isolation by suppressing unwanted wavelengths, especially artificial light pollution lines such as sodium (589 nm) and mercury (435 nm, 578 nm), as well as atmospheric skyglow.\u003c\/p\u003e\n\n\u003ch2\u003eOptical Performance and Transmission Control\u003c\/h2\u003e\n\u003cp\u003eThe filter delivers \u003cstrong\u003e80% transmission at the SII 672 nm line\u003c\/strong\u003e and provides off-band suppression down to 0.1% (OD3). It also blocks infrared wavelengths from 700–1100 nm, ensuring controlled spectral response and improved imaging precision.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eNot suitable for solar observation or imaging.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003ch2\u003ePrecision Construction and Filter Cell\u003c\/h2\u003e\n\u003cp\u003eManufactured using \u003cstrong\u003eSchott optical glass\u003c\/strong\u003e with a 2.0 mm substrate thickness, the filter meets strict optical tolerances for flatness and parallelism. The \u003cstrong\u003eultra-slim filter cell\u003c\/strong\u003e minimizes vignetting and maximizes clear aperture (26 mm for 1.25\"). The Aerometal CNC-machined housing features black anodized finishing and internal anti-reflection treatment to reduce stray light.\u003c\/p\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eFilter Type\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003eSII Narrowband\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eCentral Wavelength\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003e672 nm\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eBandwidth\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003e6.5 nm\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eTransmission at SII\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003e80%\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eOff-Band Transmission\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003e0.1% (OD3)\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eIR Blocking\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003e700–1100 nm\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eSubstrate Material\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003eSchott optical glass\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eThickness\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003e2.0 mm\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eSurface Quality\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003e60\/40 (MIL-O-13830)\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eFlatness\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003e1\/4 λ\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eParallelism\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003e\u0026lt; 30″\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eFormat\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003e1.25\" (31.8 mm)\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e\u003cstrong\u003eClear Aperture\u003c\/strong\u003e\u003c\/td\u003e\u003ctd\u003e26 mm\u003c\/td\u003e\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eOptolong SII 6.5nm 1.25\"\u003c\/strong\u003e is a precision-engineered solution for narrowband deep-sky imaging, ideal for emission nebula photography and advanced SHO astrophotography workflows.\u003c\/p\u003e","brand":"Optolong","offers":[{"title":"Default Title","offer_id":51261494591819,"sku":"OPSII-1","price":169.0,"currency_code":"EUR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0886\/1981\/1147\/files\/filtro_sii_6.5nm_ccd_nebulose_672nm_optolong_31.8mm_italia.jpg?v=1744220910","url":"https:\/\/adriasky.it\/en\/products\/optolong-sii-filter-6-5nm-1-25-inch","provider":"Adriasky","version":"1.0","type":"link"}