{"product_id":"antlia-oiii-2-5nm-ultra-narrowband-filter","title":"Antlia OIII 2.5nm Ultra Narrowband Filter","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eIsolates the 500.7nm OIII emission line\u003c\/li\u003e\n\u003cli\u003e2.5nm (+0.3\/-0.1nm) FWHM ultra-narrowband design\u003c\/li\u003e\n\u003cli\u003e\u0026gt;=92% peak transmission at the central wavelength\u003c\/li\u003e\n\u003cli\u003e\u0026gt;=OD5 (0.001%) blocking of off-band wavelengths\u003c\/li\u003e\n\u003cli\u003eRecommended for systems f\/3.5 or slower\u003c\/li\u003e\n\u003cli\u003eThermally stable 2mm quartz glass substrate\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\u003eAntlia OIII 2.5nm Ultra Narrowband Filter\u003c\/h2\u003e\n\u003cp\u003eThe Antlia OIII 2.5nm Ultra Narrowband Filter isolates the critical 500.7nm oxygen-III emission line with an extremely tight 2.5nm full-width half-maximum (FWHM) bandpass. This filter achieves a peak transmission of \u0026gt;=92% at the central wavelength, while deep \u0026gt;=OD5 (0.001%) out-of-band blocking blocks interference from other wavelengths. Built on a 2mm thick quartz glass substrate, it is recommended for optical systems f\/3.5 or slower for best optical performance.\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 2.5nm FWHM Advantage: Maximizing Signal-to-Noise Ratio\u003c\/h3\u003e\n\u003cp\u003eThe defining feature of this filter is its ultra-narrow 2.5nm bandpass. By rejecting a greater portion of the background skyglow from moonlight and artificial light pollution, the filter increases the contrast between your target nebula and the sky. Antlia states the narrow FWHM results in an exceptionally high signal-to-noise ratio for deep sky photography, helping you capture fainter details.\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\u003e\u0026gt;=92% Peak Transmission with a Flat-Top Spectrum\u003c\/h3\u003e\n\u003cp\u003eThis filter has a specified peak transmission of \u0026gt;=92% at the 500.7nm OIII line. Its flat-top spectral profile provides a wider \"shoulder\" of peak transmission around the central wavelength. Antlia states this design minimizes the loss in transmission due to the central wavelength (CWL) shift that occurs in faster optical systems.\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 on a Thermally Stable Quartz Substrate\u003c\/h3\u003e\n\u003cp\u003eThe filter's \u0026gt;=OD5 (0.001%) out-of-band blocking is designed to block interference from other wavelengths and minimize halos around bright stars. The filter is built on a quartz glass substrate, which has an ultra-low thermal expansion coefficient with outstanding thermal and mechanical properties. All filters are coated to the edge and unmounted versions are edge-blackened to eliminate internal reflections.\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\u003eAntlia 2.5nm Ultra vs. 3nm Pro: A 20-30% Signal Boost\u003c\/h3\u003e\n\u003cp\u003eCompared to Antlia's 3nm Pro series, the 2.5nm Ultra series offers a quantifiable imaging advantage. Coated on quartz glass, the Ultra filters have higher transmittance for the emission lines and a narrower FWHM, and Antlia estimates they improve signal by 20-30% in your images. Antlia adds that the narrower FWHM results in an exceptionally high signal-to-noise ratio for deep sky photography.\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 main benefit of the Antlia 2.5nm OIII filter over a 3nm or 5nm version?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe primary benefit of the \u003cstrong\u003e2.5nm\u003c\/strong\u003e bandpass is higher contrast. By blocking more of the background skyglow from light pollution and moonlight, it produces a darker background and makes faint nebular details stand out more clearly. Compared with its own 3nm Pro series, Antlia also states higher transmittance and estimates a 20-30% signal improvement.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Antlia 2.5nm OIII filter with my f\/4 telescope?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. Antlia recommends the filter for optics of \u003cstrong\u003ef\/3.5 or slower\u003c\/strong\u003e, and f\/4 is within that range. Faster optics cause a slight blue-shift in the filter's passband, and the \u003cstrong\u003eflat-top spectrum\u003c\/strong\u003e design minimizes the loss in transmission from that shift.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the quartz substrate in the Antlia 2.5nm OIII filter improve my images?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003equartz glass substrate\u003c\/strong\u003e has an ultra-low thermal expansion coefficient with excellent thermal stability. Antlia states it also gives better fracture and scratch resistance and improved coating resilience to cleaning, for remarkable durability in challenging environmental conditions.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the Antlia 2.5nm OIII filter control halos on bright stars?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe filter's deep \u003cstrong\u003e\u0026gt;=OD5 (0.001%) blocking\u003c\/strong\u003e of wavelengths outside the passband is designed by Antlia to block interference from other wavelengths and minimize halos around bright stars.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does the \"flat-top spectrum\" of the Antlia 2.5nm OIII filter mean in practice?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA \u003cstrong\u003eflat-top spectrum\u003c\/strong\u003e means the filter has a broad, level plateau of high transmission across its passband, rather than a sharp peak. This makes the filter more tolerant of the slight wavelength shifts that occur with faster telescope optics; Antlia states it minimizes the loss in transmission due to that shift.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is the Antlia OIII 2.5nm filter not recommended for visual observation?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAntlia lists night visual observation as not recommended. The \u003cstrong\u003e2.5nm bandpass\u003c\/strong\u003e passes only a very small slice of the spectrum, which suits a camera sensor during long exposures but leaves little light for the eye. Antlia also lists solar imaging as not recommended. \u003cstrong\u003eDO NOT LOOK AT THE SUN WITH THIS FILTER. Serious eye damage will result if you fail to observe the warning.\u003c\/strong\u003e\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\u003eOIII Ultra Narrowband (SHO 2.5nm Ultra series)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCentral Wavelength (CWL)\u003c\/td\u003e\n\u003ctd\u003e500.7nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFull Width Half Maximum (FWHM)\u003c\/td\u003e\n\u003ctd\u003e2.5nm +0.3\/-0.1nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePeak Transmission\u003c\/td\u003e\n\u003ctd\u003e\u0026gt;=92% at 500.7nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBlocking\u003c\/td\u003e\n\u003ctd\u003e\u0026gt;=OD5 (0.001%) out of band\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpectrum Profile\u003c\/td\u003e\n\u003ctd\u003eFlat-top\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRecommended F-Ratio\u003c\/td\u003e\n\u003ctd\u003ef\/3.5 or slower\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSubstrate\u003c\/td\u003e\n\u003ctd\u003eQuartz glass\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Thickness\u003c\/td\u003e\n\u003ctd\u003e2mm (+\/-0.05mm on 2\" mounted, +\/-0.1mm on 36mm unmounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eEdge Finish\u003c\/td\u003e\n\u003ctd\u003eCoated to the edge; unmounted filters are edge blackened\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Formats\u003c\/td\u003e\n\u003ctd\u003e2\" Mounted (M48x0.75), 36mm Round Unmounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eQuality Control\u003c\/td\u003e\n\u003ctd\u003e100% of production individually scanned\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNot Recommended For\u003c\/td\u003e\n\u003ctd\u003eSolar imaging, night visual observation\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\"\u003eActual measured spectrum, transmission and blocking (OD) data for the filter\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\n3-Year Warranty against delamination.\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Antlia","offers":[{"title":"36mm Round Unmounted","offer_id":51932625109277,"sku":"ANT-OIII-2.5NM-RD36","price":465.0,"currency_code":"USD","in_stock":true},{"title":"2\" Mounted","offer_id":51932625142045,"sku":"ANT-OIII-2.5NM-2","price":590.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/antlia-src-omvGapwUw6Ac46Ac_cd8a3c89-0fab-449f-a3e4-f0f984f561fb.jpg?v=1792550003","url":"https:\/\/davidastro.com\/en-int\/products\/antlia-oiii-2-5nm-ultra-narrowband-filter","provider":"David Astro","version":"1.0","type":"link"}