{"product_id":"explore-scientific-310120","title":"Explore Scientific Nebula Filter S-II 2-inch 6.5nm","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e6.5nm Narrow Bandpass\u003c\/li\u003e\n\u003cli\u003eTargets the 672nm Ionized Sulfur (S-II) Emission Line\u003c\/li\u003e\n\u003cli\u003e2-inch Barrel Diameter for Larger Focusers\u003c\/li\u003e\n\u003cli\u003eDrastically Increases Contrast on Emission Nebulae\u003c\/li\u003e\n\u003cli\u003eIncludes Individual Test Report for Quality Assurance\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eExplore Scientific Nebula Filter S-II 2-inch 6.5nm\u003c\/h2\u003e\n\u003cp\u003eThe Explore Scientific Nebula Filter S-II 2-inch 6.5nm isolates the critical 672nm emission line from ionized sulfur, a key signal in many deep-sky objects. Its extremely narrow 6.5nm bandpass aggressively blocks broadband light pollution, transmitting only the specific wavelength produced by emission nebulae and supernova remnants to reveal faint, hidden structures.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003e6.5nm Bandpass: Isolating the 672nm S-II Emission Line\u003c\/h3\u003e\n\u003cp\u003eThis filter is engineered to transmit light almost exclusively within a 6.5nm window centered on the 672nm wavelength of ionized sulfur (S-II). By rejecting virtually all other wavelengths, including common sources of artificial light like streetlamps, it dramatically darkens the sky background. This boosts the contrast of nebulae that glow in S-II, making previously invisible details stand out for both visual observation and astrophotography.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eA 2-inch Solution for High-Contrast Nebula Observation\u003c\/h3\u003e\n\u003cp\u003eFrom city suburbs to moderately dark sites, light pollution can wash out the delicate structures of deep-sky objects. The Explore Scientific S-II filter restores that lost contrast, allowing you to see and image targets like planetary nebulae and supernova remnants with surprising clarity. The 2-inch format is ideal for imagers using larger focusers and camera setups, ensuring no vignetting of the light cone.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eS-II vs. H-alpha: Completing the Astrophotography Palette\u003c\/h3\u003e\n\u003cp\u003eWhile an H-alpha filter captures the dominant hydrogen signal that forms the primary structure of most emission nebulae, the S-II filter reveals different information. Ionized sulfur often traces regions of different temperatures and densities, highlighting shock fronts and intricate details that can be missed in H-alpha alone. For astrophotographers creating false-color images, S-II data is an essential component for producing the \"Hubble Palette\" (SHO), adding depth and scientific context to the final image.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the main purpose of the Explore Scientific S-II 2-inch 6.5nm filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe primary purpose of this filter is to increase the contrast of emission nebulae by isolating the specific light they emit from ionized sulfur (the \u003cstrong\u003eS-II line at 672nm\u003c\/strong\u003e). It aggressively blocks out light pollution, making it possible to observe and photograph faint deep-sky structures, even from urban or suburban locations.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the S-II 6.5nm filter improve views of the Eagle Nebula (M16) from a light-polluted area?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Eagle Nebula (M16) is rich in ionized gases, including sulfur. From a light-polluted site, the nebula can appear as a faint, indistinct smudge. The \u003cstrong\u003eExplore Scientific S-II 6.5nm filter\u003c\/strong\u003e blocks the overwhelming glow from city lights and allows only the 672nm S-II light from the nebula to pass, dramatically darkening the background and making the iconic \"Pillars of Creation\" and surrounding nebulosity much more visible.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the S-II 2-inch filter for visual observing, or is it just for photography?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile narrowband filters like S-II are most famously used in astrophotography, they are also effective for visual use, especially on larger aperture telescopes (typically 8 inches or more). The extreme contrast boost can make faint planetary nebulae and supernova remnants \"pop\" into view where they were previously invisible. However, the image will be dim, as the filter passes very little light.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eFor my 10\" f\/8 Ritchey-Chrétien, when would I choose this S-II filter over a standard light pollution filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA standard light pollution (LPR) filter passes broad bands of the spectrum and is good for general viewing of galaxies and star clusters. You would choose the \u003cstrong\u003eExplore Scientific S-II 6.5nm filter\u003c\/strong\u003e specifically when targeting \u003cstrong\u003eemission nebulae\u003c\/strong\u003e. The S-II filter provides far more aggressive rejection of light pollution for these specific targets, delivering much higher contrast on objects like the Veil Nebula (NGC 6960) or the Crescent Nebula (NGC 6888) than a general-purpose LPR filter can.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is this S-II filter 6.5nm and not wider, like 12nm?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA narrower bandpass like \u003cstrong\u003e6.5nm\u003c\/strong\u003e provides superior performance in heavily light-polluted skies. It rejects more of the unwanted artificial light that falls near the desired S-II emission line. While a wider filter might produce a slightly brighter image, the 6.5nm design delivers a darker background and higher contrast, which is critical for teasing out the faintest details.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does the individual test report for the Explore Scientific S-II filter tell me?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe included individual test report is your assurance of the filter's quality. It provides a graph showing the exact transmission characteristics of your specific filter, confirming that its bandpass is centered correctly on the \u003cstrong\u003e672nm S-II line\u003c\/strong\u003e and meets the specified \u003cstrong\u003e6.5nm\u003c\/strong\u003e width. This guarantees you are receiving a filter that performs to specification.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/explore-scientific-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eExplore Scientific Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":52909388661021,"sku":"ES-310120","price":299.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/ExploreScientific-Nebula-Filter-S-II-2-inch-6-5nm-1_6077ea2b-6aa8-4dae-8d7d-6ddf9c789049.jpg?v=1789061566","url":"https:\/\/davidastro.com\/en-us\/products\/explore-scientific-310120","provider":"David Astro","version":"1.0","type":"link"}