{"product_id":"optolong-sii-6-5nm-narrowband-filter","title":"Optolong SII 6.5nm Narrowband Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eIsolates the Sulfur-II (SII) emission line at 672nm\u003c\/li\u003e\n\u003cli\u003eTight 6.5nm bandpass for maximum contrast\u003c\/li\u003e\n\u003cli\u003eEnables imaging in heavily light-polluted skies and during bright moonlight\u003c\/li\u003e\n\u003cli\u003eAdvanced ion-assisted multi-layer coatings for durability and stability\u003c\/li\u003e\n\u003cli\u003eAvailable in 1.25\" Mounted, 2\" Mounted, and 36mm Unmounted sizes\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\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\u003eOptolong SII 6.5nm Narrowband Filter\u003c\/h2\u003e\n\u003cp\u003eThe Optolong SII 6.5nm Narrowband Filter isolates a tight 6.5nm bandpass centered on the 672nm wavelength of doubly ionized sulfur. This precision allows imagers to capture the faint, structural details in emission nebulae, separating the specific SII signal from interfering light pollution and moonlight, which is critical when a 6.5nm window is all you have to work with.\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\u003eThe 6.5nm Bandpass for Sulfur-II Emission\u003c\/h3\u003e\n\u003cp\u003eThis filter is engineered to transmit light from the specific 672nm emission line characteristic of ionized sulfur. The extremely narrow 6.5nm bandpass dramatically increases contrast by rejecting all other wavelengths, rendering the faint structures within nebulae against a dark sky background. This is essential for revealing details that are otherwise lost in the noise of broadband imaging.\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\u003eImaging Through Moonlight and City Skyglow at 672nm\u003c\/h3\u003e\n\u003cp\u003eBy targeting only the 672nm SII line, the Optolong 6.5nm filter effectively blocks common sources of light pollution, including mercury vapor and sodium vapor streetlights. It also rejects natural skyglow from neutral oxygen emission, allowing you to continue imaging even under a full moon. This transforms weeks of potential downtime into productive imaging sessions, maximizing your time under the stars regardless of your location.\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\u003eThe \"S\" in the Hubble Palette: Building Full-Color Narrowband Images\u003c\/h3\u003e\n\u003cp\u003eThe SII 6.5nm filter is a critical component of the \"SHO\" narrowband imaging trio, alongside Hydrogen-alpha and Oxygen-III filters. By assigning the data from each filter to a different color channel (Sulfur to Red, Hydrogen to Green, Oxygen to Blue), you can create the vibrant, high-contrast images famously associated with the Hubble Space Telescope. This technique reveals the chemical composition and structure of targets like the Pillars of Creation in the Eagle Nebula (M16).\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\u003eIon-Assisted Coatings for 6.5nm Stability and Durability\u003c\/h3\u003e\n\u003cp\u003eOptolong utilizes an advanced ion-assisted deposition coating process to ensure the filter's optical characteristics are precise and long-lasting. This technology produces a dense, scratch-resistant coating and guarantees the stability of the central wavelength (CWL). The 6.5nm bandpass will not deviate due to temperature changes during an imaging session, ensuring consistent, reliable data from dusk till dawn.\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 primary use for the Optolong SII 6.5nm filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Optolong SII 6.5nm filter is designed for astrophotography of emission nebulae. It isolates the light emitted by ionized sulfur at a wavelength of 672nm, which dramatically increases the contrast of these objects, especially when used from light-polluted areas or as part of a multi-filter color composite image.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the 6.5nm bandpass on the Optolong SII filter improve my images?\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 rejects more unwanted light from streetlights, moonlight, and natural skyglow compared to wider filters. This results in a darker sky background and higher contrast between your target nebula and the sky, allowing fainter details to be captured.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Optolong SII 6.5nm filter for visual observing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this filter is not recommended for visual use. The 6.5nm bandpass is so restrictive that it blocks nearly all visible light, making it impossible to see all but the very brightest nebulae. It is designed specifically for long-exposure imaging with sensitive astronomy cameras.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the Optolong SII 6.5nm filter perform on the Rosette Nebula (NGC 2244) from a light-polluted location?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Rosette Nebula has significant Sulfur-II emission. Using the Optolong SII 6.5nm filter from a suburban or city location will allow you to capture the delicate filamentary structures within the nebula that would normally be completely washed out by skyglow. It is an essential tool for revealing the full structure of this and similar star-forming regions.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat other filters do I need with the Optolong SII 6.5nm for full-color narrowband imaging?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eFor full-color \"Hubble Palette\" (SHO) imaging, you will need two other narrowband filters:\n\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHydrogen-alpha (H-alpha) filter:\u003c\/strong\u003e Captures ionized hydrogen, typically the strongest signal.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOxygen-III (OIII) filter:\u003c\/strong\u003e Captures ionized oxygen, which reveals high-energy regions.\u003c\/li\u003e\n\u003c\/ul\u003e\nCombining data from these three filters allows you to create detailed and scientifically interesting false-color images.\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the Optolong SII 6.5nm filter work well with my fast f\/4 Newtonian telescope?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile narrowband filters perform optimally with slower focal ratios, Optolong's advanced coatings provide excellent stability. With very fast optical systems (f\/4 and below), some narrowband filters can exhibit a slight shift in their central wavelength. However, the Optolong SII 6.5nm is widely used with fast telescopes and produces excellent results. For critical applications, ensure your imaging software can accommodate precise focus for each filter.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003eNarrowband Interference Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBandpass\u003c\/td\u003e\n\u003ctd\u003e6.5nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCentral Wavelength\u003c\/td\u003e\n\u003ctd\u003e672nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePrimary Emission Line\u003c\/td\u003e\n\u003ctd\u003eSulfur-II (SII)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoating Technology\u003c\/td\u003e\n\u003ctd\u003eIon-Assisted Multi-layer Deposition\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSubstrate\u003c\/td\u003e\n\u003ctd\u003eOptical Glass\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\" Mounted, 2\" Mounted, 36mm Unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eOptolong SII 6.5nm Narrowband Filter (Selected Size)\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eProtective Case\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/optolong-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eOptolong 3-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Optolong","offers":[{"title":"1.25\" Mounted","offer_id":52941916373277,"sku":"OPT-11401","price":159.0,"currency_code":"USD","in_stock":true},{"title":"2\" Mounted","offer_id":52941916406045,"sku":"OPT-11402","price":229.0,"currency_code":"USD","in_stock":true},{"title":"36mm Round Unmounted","offer_id":52941916438813,"sku":"OPT-11404","price":189.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Optolong-SII-6-5nm-imaging-narrow-band-filter-for-nebulae-photography-1_667ac9a4-9af1-4d52-a692-799938db0908.jpg?v=1789592369","url":"https:\/\/davidastro.com\/fr-us\/products\/optolong-sii-6-5nm-narrowband-filter","provider":"David Astro","version":"1.0","type":"link"}