{"product_id":"baader-c2-swan-band-comet-filter-15nm","title":"Baader C2 Swan-Band Comet Filter (15nm)","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eIsolates Diatomic Carbon (C2) Swan Bands at 511nm \u0026amp; 514nm\u003c\/li\u003e\n\u003cli\u003e≤ 15nm Passband Width\u003c\/li\u003e\n\u003cli\u003eComplete OIII Emission Line Blocking\u003c\/li\u003e\n\u003cli\u003eCMOS-Optimized with Reflex-Blocker™ Coatings\u003c\/li\u003e\n\u003cli\u003eLife-Coat™ Sealed Coating Edges for Durability\u003c\/li\u003e\n\u003cli\u003ePlaneoptically Polished Substrate\u003c\/li\u003e\n\u003cli\u003eAvailable in 1.25\" and 2\" Mounted Formats\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\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\u003eIsolate the Ghostly Glow — The Baader C2 Swan-Band Comet Filter\u003c\/h2\u003e\n\u003cp\u003eThe Baader C2 Swan-Band Comet Filter is built around a single, demanding trade-off: achieving the highest possible contrast on cometary gas tails by isolating the faint C2 emission lines while aggressively rejecting all other signals, including the strong OIII line that contaminates competing designs. This is not a general-purpose nebula filter. It is a specialist tool engineered for the dedicated comet observer and imager who needs to pull the delicate, evolving structure of a gas tail out from the glow of the coma and the background sky.\u003c\/p\u003e\n\u003cp\u003eUnlike broadband or even standard nebula filters that offer a general contrast boost, the Swan-Band filter targets the specific physics of a comet. As a comet nears the sun, solar radiation causes its nucleus to outgas, creating a cloud of molecules. The most prominent emission in the visible spectrum from this gas tail comes from diatomic carbon (C2), which radiates strongly at 511nm and 514nm. This filter is your narrow window into that specific phenomenon, turning a faint smudge into a detailed structure.\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\u003eTargeted C2 Swan-Band Passband\u003c\/h3\u003e\n\u003cp\u003eThe core of the filter is its narrow passband, with a full-width at half-maximum (FWHM) of 15nm or less, centered at 512nm. This window is precisely tuned to capture the two bright C2 \"Swan Bands\" that give a gas tail its characteristic teal or blue-green glow. By accepting light almost exclusively from this molecular emission, the filter dramatically darkens the sky background, making faint tail streamers and condensations visible where they were previously lost in the noise.\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 Critical OIII Blocking Advantage\u003c\/h3\u003e\n\u003cp\u003eThe defining feature of Baader's design is its complete rejection of the Oxygen-III (OIII) emission line at 501nm. Many other filters designed for comets allow this line to pass, but OIII is not a significant component of a comet's gas tail. By including it, other filters brighten the background skyglow and the comet's dust coma, which reduces the specific contrast of the gas tail. Baader’s OIII-blocking approach ensures the only thing you see is the C2 emission, resulting in a darker field and higher-contrast tail 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\u003eEngineered for Modern CMOS Sensors\u003c\/h3\u003e\n\u003cp\u003eModern CMOS sensors are notoriously reflective, often creating halos and internal reflections when paired with traditional filters. The Baader Swan-Band filter features fully optimized coatings that are angled to prevent light from bouncing between the filter and the sensor cover glass. This meticulous attention to reflection suppression means you can capture long exposures of a bright cometary nucleus next to a faint tail without the image being compromised by artifacts.\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\u003eReflex-Blocker™ and Life-Coat™ Durability\u003c\/h3\u003e\n\u003cp\u003eBaader’s proprietary Reflex-Blocker™ hard coatings provide superior transmission and anti-reflection properties, while their Life-Coat™ process seals the coating layers at the very edge of the glass. This is a critical, often overlooked feature that provides long-term durability. The sealed edges are impervious to moisture, preventing the slow degradation that can affect lesser filters after years of use in damp, real-world observing conditions.\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\u003ePreserving Optical Integrity with a Planeoptically Polished Substrate\u003c\/h3\u003e\n\u003cp\u003eA filter is useless if it degrades the quality of your telescope's optics. Each Swan-Band filter is made from a fine-optically polished glass substrate, ensuring it is perfectly flat and parallel. This means it will not introduce astigmatism or other aberrations into the light path, preserving the pinpoint sharpness of stars and the finest details within the comet's structure. Your telescope's resolution is maintained, not compromised.\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\u003eMaximum Contrast from Blackened Edges\u003c\/h3\u003e\n\u003cp\u003eTo wring out every last bit of contrast, the edges of the filter glass are carefully blackened. This simple step prevents stray light from entering the side of the glass and reflecting internally into the eyepiece or camera sensor. It is one more small, but important, detail that contributes to a genuinely dark background and makes the faintest cometary features stand out.\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\u003eObserving Comet C\/2023 A3 (Tsuchinshan-ATLAS)\u003c\/h3\u003e\n\u003cp\u003eImagine observing a bright comet as it makes its closest approach. Visually, without a filter, you see a bright, fuzzy coma and a hint of a tail. Now, thread in the Baader Swan-Band filter. The bright, dominant dust tail and coma dim significantly, and the sky background turns nearly black. As your eye adapts, the faint, blue-green gas tail begins to emerge, not as a uniform streak, but as a collection of fine, interwoven streamers and knots, revealing the dynamic interaction between the comet and the solar wind.\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\"\u003eWill the Swan-Band filter help me see any comet?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis filter is most effective on comets that have a significant gas tail, which is rich in diatomic carbon. For comets that are dominated by a dust tail, which simply reflects sunlight, the filter will provide little to no contrast enhancement and will dim the view.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy does blocking OIII matter for a comet filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eBlocking OIII is critical because it's a major component of natural and artificial skyglow, but not a major emission from comets. By blocking it, the filter darkens the background sky and the comet's coma without dimming the C2 gas tail, dramatically increasing the tail's contrast.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Baader Swan-Band filter for nebula observing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this filter is not recommended for nebulae. It is designed to block the primary nebula emission lines like OIII and Hydrogen-beta. Using it on a nebula would result in a very dim, unsatisfactory view. It is a highly specialized tool for comets.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs this filter better for visual use or for imaging?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eIt excels at both. For visual observers, it provides a dramatic increase in gas tail contrast. For imagers using monochrome or color CMOS cameras, it isolates the C2 signal for a dedicated luminance channel or enhances the green\/blue channel data for a more detailed and colorful final image.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the main trade-off of using this filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe primary trade-off is its specialization. It significantly dims the comet's dust tail and nucleus to enhance the gas tail. You are choosing to sacrifice the view of the whole object to see extreme detail in one specific part of it.\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\u003eBandpass Comet Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCentral Wavelength\u003c\/td\u003e\n\u003ctd\u003e512nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eHalf-Bandwidth (FWHM)\u003c\/td\u003e\n\u003ctd\u003e≤ 15nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePrimary Transmission\u003c\/td\u003e\n\u003ctd\u003eC2 (Diatomic Carbon) at 511nm and 514nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBlocking\u003c\/td\u003e\n\u003ctd\u003eComplete OIII line blocking at 501nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSubstrate\u003c\/td\u003e\n\u003ctd\u003ePlaneoptically Polished Glass\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoatings\u003c\/td\u003e\n\u003ctd\u003eCMOS-Optimized, Reflex-Blocker™ Hard Coatings\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDurability Features\u003c\/td\u003e\n\u003ctd\u003eLife-Coat™ Hermetically Sealed Edges\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOther Features\u003c\/td\u003e\n\u003ctd\u003eBlackened Lens Edges\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\" and 2\" cell mounted\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\u003cimg class=\"DAV-img-box\" alt=\"Baader C2 Swan-Band Comet Filter in protective case\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Baader-Swan-Band-Filter.jpg\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBaader C2 Swan-Band Comet Filter\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\u003cimg class=\"DAV-img-box\" alt=\"Baader filter storage case\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Baader-Filter-Case.jpg\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eFilter Storage 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\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/zwo-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"1.25\" Mounted","offer_id":51320832950557,"sku":"BAA-2961860","price":116.0,"currency_code":"CAD","in_stock":true},{"title":"2\" Mounted","offer_id":51320832983325,"sku":"BAA-2961860","price":232.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Baader-Swan-Band-Comet-Filter.jpg?v=1779478120","url":"https:\/\/davidastro.com\/products\/baader-c2-swan-band-comet-filter-15nm","provider":"David Astro","version":"1.0","type":"link"}