{"product_id":"antlia-cak-3nm-393-3nm-solar-filter-1-25","title":"Antlia CaK 3nm 393.3nm Solar Filter - 1.25\"","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eIsolates the Calcium K-line (CaK) at a central wavelength of 393.3nm\u003c\/li\u003e\n\u003cli\u003eNarrow 3nm bandpass designed to maximize contrast for high-resolution solar imaging\u003c\/li\u003e\n\u003cli\u003eOD5 (0.001%) blocking from 200-1200nm and OD3 (0.1%) from 1200-1500nm\u003c\/li\u003e\n\u003cli\u003eDesigned for imaging with cameras; not recommended for visual observation\u003c\/li\u003e\n\u003cli\u003eThe same CaK filter that screws into the Antlia Herschel Wedge prism\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\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\u003eAntlia CaK 3nm 393.3nm Solar Filter - 1.25\"\u003c\/h2\u003e\n\u003cp\u003eThe Antlia CaK 3nm 393.3nm Solar Filter isolates a specific violet wavelength to reveal the sun's lower chromosphere, a turbulent layer just above the visible surface. Its tight 3nm bandpass is centered precisely at 393.3nm to maximize contrast on sunspots and solar surface granulation. This 1.25\" filter has OD5 blocking from 200-1200nm, which Antlia says delivers superb resolution for imaging. It is the CaK filter that screws into the Antlia Herschel Wedge prism and is not a stand-alone solar filter. Never look into the Sun with the K-line filter alone: although you don't perceive it, a lot of harmful UV radiation enters your eye.\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\u003e3nm Bandpass at 393.3nm: Imaging the Lower Chromosphere\u003c\/h3\u003e\n\u003cp\u003eThis filter's performance is defined by its narrow 3nm bandpass, which is essential for isolating the faint structures visible in the Calcium-K emission line. By rejecting adjacent wavelengths, the filter increases the contrast of sunspots, solar surface granulation and other features prominent in CaK light, such as plage (bright regions around sunspots). The filter is made on a heat resistant, double-polished substrate.\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\u003eOD5 Blocking Across 200-1200nm for Maximum Contrast\u003c\/h3\u003e\n\u003cp\u003eThe Antlia CaK filter provides an optical density of OD5 (transmitting only 0.001% of out-of-band light) from 200nm to 1200nm, with OD3 (0.1%) from 1200nm to 1500nm. Antlia states this high blocking specification delivers superb resolution for imaging with the CaK 3nm filter.\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\u003eFor Cameras Only: Why the 393.3nm Line is Nearly Invisible\u003c\/h3\u003e\n\u003cp\u003eThe 393.3nm wavelength sits at the very edge of the violet spectrum, where the eye has low sensitivity and poor resolving ability, so solar features are almost invisible to human vision. The filter is not recommended for visual observation and is designed for imaging with cameras that have spectral responses well beyond human vision. \u003cstrong\u003eNever look into the Sun with the K-line filter alone: although you don't perceive it, a lot of harmful UV radiation enters your eye.\u003c\/strong\u003e\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\"\u003eWhy can't I use the Antlia CaK 3nm filter for visual solar observing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe filter transmits light at the \u003cstrong\u003e393.3nm wavelength\u003c\/strong\u003e, which is in the deep violet part of the spectrum. The human eye has very poor sensitivity and resolving ability at this frequency, making solar features nearly invisible. The filter is designed for imaging with cameras that have spectral responses well beyond human vision. \u003cstrong\u003eNever look into the Sun with the K-line filter alone: although you don't perceive it, a lot of harmful UV radiation enters your eye.\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat solar features will the Antlia CaK 393.3nm filter show me?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAntlia designs the CaK filter to maximize contrast for high-resolution imaging of features prominent in CaK light. With a camera, you can image:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSunspots:\u003c\/strong\u003e Named by Antlia as a target.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGranulation:\u003c\/strong\u003e The \"cell-like\" texture of the solar surface, named by Antlia.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlage:\u003c\/strong\u003e Bright, active regions that often surround sunspot groups.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDo I need the Antlia CaK filter if I own the Antlia Herschel Wedge?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo. This \u003cstrong\u003eCaK 3nm 393.3nm filter\u003c\/strong\u003e is screwed into the Antlia Herschel Wedge prism, so you do not need to buy it separately if you use the Antlia Herschel Wedge.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat kind of telescope do I need to use the Antlia CaK 3nm filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAntlia presents this filter only as the internal CaK filter that screws into the Antlia Herschel Wedge prism, and it does not list other telescopes or solar filters for it. It is \u003cstrong\u003enot a stand-alone solar filter\u003c\/strong\u003e and is for imaging only. \u003cstrong\u003eNever look into the Sun with the K-line filter alone: although you don't perceive it, a lot of harmful UV radiation enters your eye.\u003c\/strong\u003e Contact us before planning any other setup.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I image sunspot groups and active regions with the Antlia CaK filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. Antlia designs the \u003cstrong\u003e3nm bandpass\u003c\/strong\u003e to maximize contrast for high-resolution imaging of sunspots, solar surface granulation and other features prominent in CaK light, such as the bright plage around active regions. Results depend on your optics, camera and seeing.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I stack the 1.25\" Antlia CaK filter with a Hydrogen-alpha filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this is not a useful or safe combination. Hydrogen-alpha filters operate at 656.3nm, while this filter operates at \u003cstrong\u003e393.3nm\u003c\/strong\u003e. Stacking them would block all light from reaching the sensor. This filter is used in the Antlia Herschel Wedge prism for CaK imaging.\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\u003eCalcium K-line (CaK) solar imaging filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCentral Wavelength (CWL)\u003c\/td\u003e\n\u003ctd\u003e393.3nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBandpass\u003c\/td\u003e\n\u003ctd\u003e3nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBlocking Range 1\u003c\/td\u003e\n\u003ctd\u003eOD5 (0.001%) between 200-1200nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBlocking Range 2\u003c\/td\u003e\n\u003ctd\u003eOD3 (0.1%) between 1200-1500nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSubstrate\u003c\/td\u003e\n\u003ctd\u003eHeat resistant, double-polished\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRecommended Use\u003c\/td\u003e\n\u003ctd\u003eImaging with cameras only\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVisual Observation\u003c\/td\u003e\n\u003ctd\u003eNot recommended\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNote\u003c\/td\u003e\n\u003ctd\u003eThis is the same CaK filter that is screwed into the Antlia Herschel Wedge prism\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Sizes\u003c\/td\u003e\n\u003ctd\u003e1.25\"\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003cp\u003eContact us for warranty details.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Antlia","offers":[{"title":"1.25\"","offer_id":51932625174813,"sku":"ANT-CAK-3NM-1.25","price":269.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/antlia-src-opK6zyQUwoAY4oAY_c8a5e970-7cb5-43ea-ac50-7db88dd54c4f.jpg?v=1792550004","url":"https:\/\/davidastro.com\/fr-us\/products\/antlia-cak-3nm-393-3nm-solar-filter-1-25","provider":"David Astro","version":"1.0","type":"link"}