{"product_id":"explore-scientific-310125","title":"Explore Scientific Nebula Filter S-II 1.25-inch 6.5nm","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eIsolates the ionized sulfur (S-II) emission line at 672nm\u003c\/li\u003e\n\u003cli\u003eUltra-narrow 6.5nm bandpass for maximum contrast\u003c\/li\u003e\n\u003cli\u003eStandard 1.25-inch barrel size fits most eyepieces and accessories\u003c\/li\u003e\n\u003cli\u003eBlocks light pollution and other interfering wavelengths\u003c\/li\u003e\n\u003cli\u003eIncludes an 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 1.25-inch 6.5nm\u003c\/h2\u003e\n\u003cp\u003eThe Explore Scientific S-II Nebula Filter isolates the specific 672nm emission line from ionized sulfur using an exceptionally narrow 6.5nm bandpass. Designed for the standard 1.25-inch format, this filter dramatically increases contrast on specific deep-sky objects by rejecting virtually all other sources of light, especially artificial light pollution.\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\u003eIsolating Ionized Sulfur: The 6.5nm Bandpass at 672nm\u003c\/h3\u003e\n\u003cp\u003eThis filter is engineered to transmit light only within a 6.5nm window centered on the 672nm wavelength characteristic of ionized sulfur. This extreme selectivity is the key to defeating light pollution; by blocking streetlights and skyglow, the filter reveals the faint signal of the nebula against a much darker background. Each Explore Scientific filter includes an individual test report, verifying that its bandpass meets the precise specification required for this high-contrast observation.\u003c\/p\u003e\n\u003cp\u003eThe primary trade-off of such a narrow filter is that it significantly dims stars, which can make locating your target via star-hopping more challenging. However, for revealing the hidden structure within emission nebulae, the benefit is transformative.\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 Contrast Boost: Revealing Faint Emission Nebulae\u003c\/h3\u003e\n\u003cp\u003eUnder a light-polluted sky, many nebulae are completely invisible. With the 6.5nm S-II filter, structures suddenly appear in areas of the sky that seemed empty moments before. It excels at making planetary nebulae, complex emission nebulae, and supernova remnants observable from urban and suburban locations.\u003c\/p\u003e\n\u003cp\u003eThis filter is a critical tool for both visual observers seeking to push their equipment to its limits and for astrophotographers. For imagers, the S-II signal provides crucial data for creating detailed, multi-wavelength color composites that reveal the chemical composition of a nebula.\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: Mapping Nebulae in Different Wavelengths\u003c\/h3\u003e\n\u003cp\u003eWhile an H-alpha filter captures the dominant hydrogen signal in most emission nebulae, an S-II filter reveals different structures and details. In astrophotography, these two filters are often used with an O-III filter to create the \"Hubble Palette\" (SHO), where each element is assigned to a different color channel.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHydrogen-alpha (H-alpha):\u003c\/strong\u003e Typically the strongest signal, revealing the primary shape and brightest areas of a nebula.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSulfur-II (S-II):\u003c\/strong\u003e Often traces regions of different temperatures and ionization, frequently highlighting the outer, wispy edges of a nebula or shock fronts that are less prominent in H-alpha. Adding S-II data provides depth and structural context that H-alpha alone cannot capture.\u003c\/li\u003e\n\u003c\/ul\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 6.5nm S-II filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eIts primary purpose is to dramatically increase the contrast of emission nebulae by isolating the light they emit from ionized sulfur (S-II) at a wavelength of \u003cstrong\u003e672nm\u003c\/strong\u003e. The narrow \u003cstrong\u003e6.5nm bandpass\u003c\/strong\u003e blocks out light pollution, allowing you to see or photograph faint nebular details that would otherwise be lost in skyglow.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the 1.25-inch S-II filter for visual observing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, absolutely. While narrowband filters like S-II are essential for astrophotography, they are also powerful tools for visual observers, especially with larger aperture telescopes (typically 8 inches or more). They can make faint supernova remnants like the Veil Nebula (NGC 6960) or details in the Lagoon Nebula (M8) pop against a dark sky background.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would this S-II filter perform on the Eagle Nebula (M16) from a suburban location?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Eagle Nebula (M16) is rich in both hydrogen and sulfur. From a suburban location, this \u003cstrong\u003e6.5nm S-II filter\u003c\/strong\u003e would be highly effective at isolating the nebula's light from city skyglow. While an H-alpha filter would show the brightest structures, the S-II filter would highlight different areas within the \"Pillars of Creation\" and surrounding nebulosity, revealing structural details that are often mapped as red or orange in Hubble Palette images.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI already have an H-alpha filter. Why do I need this Explore Scientific S-II filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAn S-II filter is the logical next step after H-alpha for any serious imager. While H-alpha captures a nebula's main structure, S-II captures a different set of physical conditions. Combining S-II data with H-alpha (and O-III) allows you to create full-color narrowband images (like the Hubble Palette) that reveal far more scientific and aesthetic detail than a monochrome H-alpha image alone.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill this 1.25\" S-II filter work with my DSLR camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA stock, unmodified DSLR camera has a built-in filter that blocks most of the deep red light at the \u003cstrong\u003e672nm\u003c\/strong\u003e S-II wavelength. To use this filter effectively for astrophotography, you need a camera that has been \"astro-modified\" to have increased red sensitivity, or a dedicated astronomy camera which is already sensitive to this wavelength.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does the included individual test report for the S-II filter guarantee?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe individual test report is your assurance of quality. It provides a chart showing the actual transmission curve for your specific filter, verifying that it meets the advertised \u003cstrong\u003e6.5nm bandpass\u003c\/strong\u003e and is correctly centered on the \u003cstrong\u003e672nm\u003c\/strong\u003e S-II wavelength. This guarantees you are getting a high-performance filter without manufacturing defects.\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":52909385515293,"sku":"ES-310125","price":280.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/ExploreScientific-Nebula-Filter-S-II-1-25-inch-6-5nm-1_debad7e9-7004-4ca6-b7c7-8ff3e4ce8cca.jpg?v=1789061537","url":"https:\/\/davidastro.com\/products\/explore-scientific-310125","provider":"David Astro","version":"1.0","type":"link"}