{"product_id":"optolong-h-alpha-3nm-filter","title":"Optolong H-alpha 3nm Narrowband Filter","description":"\n\u003c!-- short description --\u003e\n\u003cul class=\"DAV-feature-list\"\u003e\n    \u003cli\u003e\n        H-alpha 656.3nm Emission Line\n    \u003c\/li\u003e\n    \u003cli\u003e\n        3nm FWHM Bandpass\n    \u003c\/li\u003e\n    \u003cli\u003e\n        Anti-Halo Design\n    \u003c\/li\u003e\n\u003c\/ul\u003e\n\n\n\n\n\u003c!-- more --\u003e\n\n\n \u003c!-- tabs --\u003e\n\u003cul class=\"tabs\"\u003e\n    \u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n    \u003cli\u003eSpecifications\u003c\/li\u003e\n    \u003cli\u003eIn the Box\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\n\n\n\u003cul class=\"tabs-content\"\u003e\n    \u003cli class=\"active\"\u003e       \n        \u003cdiv\u003e\n            \u003c!-- Title image text --\u003e\n            \u003cdiv class=\"DAV-bg-light\"\u003e\n                \u003c!-- Main Image --\u003e\n                \u003cdiv class=\"DAV-section-center\"\u003e\n                    \u003ch2\u003eOptolong H-Alpha 3nm Narrowband Filter\u003c\/h2\u003e\n                    \u003cp\u003e The Optolong H-Alpha 3nm is a high-performance atmospheric suppression tool designed for high-resolution deep-sky imaging. By restricting the passband to a tight 3nm FWHM (Full Width at Half Maximum), this filter maximizes the signal-to-noise ratio (SNR) of the 656.3nm emission line while aggressively rejecting broadband interference from both artificial light pollution and natural airglow. \u003c\/p\u003e\n                \u003c\/div\u003e\n            \u003c\/div\u003e\n\n              \u003c!-- Title image text --\u003e\n              \u003cdiv class=\"DAV-bg-light\"\u003e\n                \u003c!-- Main Image --\u003e\n                \u003cdiv class=\"DAV-section-center\"\u003e\n                    \u003ch3\u003eThe H-Alpha (Hα) Emission Line\u003c\/h3\u003e\n                    \u003cp\u003e In the vacuum of space, ionized hydrogen atoms emit photons at specific energy levels. The most critical for astrophotography is the Hydrogen-alpha line at 656.3nm. This wavelength is the primary indicator of HII regions—massive clouds of ionized gas where star formation occurs. \u003c\/p\u003e\n                    \u003cp\u003e Because H-alpha light penetrates interstellar dust more effectively than shorter wavelengths, using a dedicated 3nm filter allows for the mapping of high-density structural filaments in emission nebulae that are typically obscured in broadband RGB imaging. \u003c\/p\u003e                   \u003c\/div\u003e\n            \u003c\/div\u003e                 \n\n\n         \u003c!-- image text --\u003e\n         \u003cdiv class=\"DAV-section-container\"\u003e\n            \u003c!-- Image Section --\u003e\n            \u003cdiv class=\"DAV-section-img\"\u003e\n                \u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Optolong-SHO-3nm-SHo-Transmission-Diagram.png?v=1770478487\" alt=\"Optolong SHO Filters Transmission Diagram\"\u003e\n            \u003c\/div\u003e\n\n            \u003c!-- Text Section --\u003e\n            \u003cdiv class=\"DAV-section-text\"\u003e\n                \u003ch3\u003e3nm FWHM: Signal Isolation and Contrast\u003c\/h3\u003e                \n                \u003cp\u003e The transition from a standard 7nm filter to a 3nm bandwidth provides a measurable increase in contrast by narrowing the \"window\" of permitted light: \u003c\/p\u003e \u003cul\u003e \u003cli\u003e\n\u003cstrong\u003eSky Background Suppression:\u003c\/strong\u003e The narrower window reduces the amount of background skyglow and moonlight reaching the sensor. This results in a significantly lower noise floor, allowing for longer sub-exposures and the detection of faint nebulosity.\u003c\/li\u003e \u003cli\u003e\n\u003cstrong\u003eStar Diameter Reduction:\u003c\/strong\u003e By cutting out the continuum light around the H-alpha peak, star bloat is minimized. This produces tighter stellar profiles, ensuring that bright stars do not overwhelm the fine details of the nebular gas.\u003c\/li\u003e \u003cli\u003e\n\u003cstrong\u003eUrban Imaging:\u003c\/strong\u003e The 3nm passband is narrow enough to allow for high-contrast imaging even in Bortle 8 or 9 environments, as it effectively isolates the target signal from the overlapping spectra of high-pressure sodium and mercury vapor lamps.\u003c\/li\u003e \u003c\/ul\u003e\n            \u003c\/div\u003e\n        \u003c\/div\u003e\n\n\n             \u003c!-- Title image text --\u003e\n             \u003cdiv class=\"DAV-bg-light\"\u003e\n                \u003c!-- Main Image --\u003e\n                \u003cdiv class=\"DAV-section-center\"\u003e\n                    \u003ch3\u003eIon-Assisted Deposition (IAD) and Thermal Stability\u003c\/h3\u003e\n                    \u003cp\u003e Optolong utilizes Ion-Assisted Deposition (IAD) to apply the interference coatings. This vacuum-deposition process results in a high-density coating that is superior to standard evaporated films. \u003c\/p\u003e\n                    \u003cul\u003e \u003cli\u003e\n\u003cstrong\u003eZero CWL Shift:\u003c\/strong\u003e Precision narrowband filters can suffer from a shift in the Central Wavelength (CWL) due to temperature fluctuations. IAD technology ensures the coating is mechanically stable, keeping the 3nm window locked on 656.3nm throughout extreme temperature drops.\u003c\/li\u003e \u003cli\u003e\n\u003cstrong\u003eDurability:\u003c\/strong\u003e The resulting surface is physically hardened, making the filter resistant to the delamination and aging effects caused by humidity and environmental exposure.\u003c\/li\u003e \u003c\/ul\u003e\n                \u003c\/div\u003e\n            \u003c\/div\u003e       \n\n             \u003c!-- Title image text --\u003e\n             \u003cdiv class=\"DAV-bg-light\"\u003e\n                \u003c!-- Main Image --\u003e\n                \u003cdiv class=\"DAV-section-center\"\u003e\n                    \u003ch3\u003eOptical Design and Halo Mitigation\u003c\/h3\u003e\n                    \u003cp\u003e A common failure in narrowband filters is the presence of internal reflections around bright stars. The Optolong 3nm series utilizes a non-cemented optical substrate. By manufacturing the filter from a single piece of high-quality optical glass rather than laminating multiple layers, the number of internal reflective surfaces is halved. \u003c\/p\u003e \u003cp\u003e When combined with precision anti-reflection (AR) coatings, this design ensures that the H-alpha signal is transmitted with \u0026gt;90% efficiency while maintaining an optical density of \u0026gt;OD4 in the out-of-band regions, virtually eliminating reflections and halos. \u003c\/p\u003e\n                \u003c\/div\u003e\n            \u003c\/div\u003e      \n\n\n        \u003c\/div\u003e\n    \u003c\/li\u003e\n\n\n\n\n    \u003cli\u003e\n        \u003ctable class=\"DAV-specifications\"\u003e\n            \u003ctbody\u003e\n              \u003ctr\u003e\n                \u003ctd\u003eCentral Wavelength (CWL)\u003c\/td\u003e\n                \u003ctd\u003e656.3 nm\u003c\/td\u003e\n              \u003c\/tr\u003e\n              \u003ctr\u003e\n                \u003ctd\u003eFWHM (Bandwidth)\u003c\/td\u003e\n                \u003ctd\u003e3 nm\u003c\/td\u003e\n              \u003c\/tr\u003e\n              \u003ctr\u003e\n                \u003ctd\u003ePeak Transmission\u003c\/td\u003e\n                \u003ctd\u003e\u0026gt;90%\u003c\/td\u003e\n              \u003c\/tr\u003e\n              \u003ctr\u003e\n                \u003ctd\u003eBlocking Range\u003c\/td\u003e\n                \u003ctd\u003e300–1100 nm\u003c\/td\u003e\n              \u003c\/tr\u003e\n              \u003ctr\u003e\n                \u003ctd\u003eOptical Density (OD)\u003c\/td\u003e\n                \u003ctd\u003e\u0026gt;OD4\u003c\/td\u003e\n              \u003c\/tr\u003e\n              \u003ctr\u003e\n                \u003ctd\u003eSubstrate\u003c\/td\u003e\n                \u003ctd\u003ePolished Optical Glass\u003c\/td\u003e\n              \u003c\/tr\u003e\n              \u003ctr\u003e\n                \u003ctd\u003eSurface Quality\u003c\/td\u003e\n                \u003ctd\u003e60\/40 (MIL-O-13830)\u003c\/td\u003e\n              \u003c\/tr\u003e\n            \u003c\/tbody\u003e\n          \u003c\/table\u003e\n          \n    \u003c\/li\u003e\n    \n\n    \u003cli\u003e\n        \u003cul class=\"DAV-grid\"\u003e\n            \u003cli class=\"DAV-grid-item\"\u003e\n                \u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Optolong-H-alpha-3nm-Filter-1.jpg?v=1770478823\" alt=\"Filter\" class=\"DAV-img-box\"\u003e\n                \u003cdiv\u003e\n                    \u003cp class=\"DAV-item-title\"\u003eFilter\u003c\/p\u003e\n                    \u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n                \u003c\/div\u003e\n            \u003c\/li\u003e\n            \u003c!-- Add more items as needed --\u003e\n        \u003c\/ul\u003e          \n    \u003c\/li\u003e\n    \n\u003c\/ul\u003e\n","brand":"Optolong","offers":[{"title":"36mm Round Unmounted","offer_id":50923151556893,"sku":"OPT-14103","price":339.0,"currency_code":"USD","in_stock":true},{"title":"2\" Mounted","offer_id":50923151589661,"sku":"OPT-14102","price":419.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Optolong-H-alpha-3nm-Filter-1.jpg?v=1770478823","url":"https:\/\/davidastro.com\/fr-us\/products\/optolong-h-alpha-3nm-filter","provider":"David Astro","version":"1.0","type":"link"}