{"title":"ZWO Narrowband Filters","description":"\u003cp\u003eZWO narrowband filters. Part of \u003ca href=\"\/collections\/zwo-filters\"\u003eZWO Filters\u003c\/a\u003e.\u003c\/p\u003e","products":[{"product_id":"zwo-narrowband-1-25-filter","title":"ZWO narrowband 1.25 filter","description":"\u003ch2 style=\"position: relative; padding: 0px 0px 10px; line-height: 28px; color: rgb(238, 57, 57); margin: 0px; font-size: 20px; font-family: \" pt sans narrow sans-serif rgb normal background-color:=\"\" font-weight:=\"\"\u003eProduct Description\u003c\/h2\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eNarrowband filter do not eliminate the effects of light pollution or increase the object s brightness. In many cases, they increase the contrast between nebula and night sky, not brightening the nebula.\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eIt can reduce the transmission of certain wavelengths of light, specifically those produced by artificial light including mercury vapor, and both high and low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow).\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eThe ZWO  H-Alpha filter  has a bandpass of  7nm and passes light at 656nm  wavelength, light transmission rate comes up to 80%. Best choice of narrowband H-alpha astrophotography filter for high-contrast imaging and revealing rich details of the nebula even in areas with strong light pollution, just prepare to experience the infinite fun with it !\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\u003ca href=\"https:\/\/astronomy-imaging-camera.com\/wp-content\/uploads\/1.25Ha.jpg\" style=\"background: transparent; color: rgb(238, 57, 57);\"\u003e\u003cimg class=\"alignnone size-large wp-image-4500\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/1.25Ha-1024x1024_6af26116-6ca5-400e-9a2c-872e8639bcd5.jpg?v=1766551095\" alt=\"1-25ha\" width=\"1024\" height=\"1024\" style=\"border: 0px; max-width: 100%; height: auto; display: block;\"\u003e\u003c\/a\u003e\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eThe ZWO narrowband S-II 7nm filter passes light at 672nm wavelength with a bandpass of 7nm which is designed for nebula observation . It is suitable for visual observation on most emission nebulae, planetary nebulae and supernova remnants, use it with H-alpha and OIII narrowband filters (SHO Set) for tricolor CCD astrophotography.\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e \u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\u003ca href=\"https:\/\/astronomy-imaging-camera.com\/wp-content\/uploads\/1.25SII.jpg\" style=\"background: transparent; color: rgb(238, 57, 57);\"\u003e\u003cimg class=\"alignnone size-large wp-image-4501\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/1.25SII-1024x1024_7e7b866f-bfc9-4799-9c7b-825784902c8b.jpg?v=1766551097\" alt=\"1-25sii\" width=\"1024\" height=\"1024\" style=\"border: 0px; max-width: 100%; height: auto; display: block;\"\u003e\u003c\/a\u003e\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eThe ZWO nrrowband O-III 7nm filter is designed for nebula observation allowing 7nm bandwidth of light centered on a wavelength of 500nm through,  which corresponds to OIII emission lines, blocking out all other light.  Adding the ZWO O-III Narrowband filter to your imaging collection will help you go beyond the RGB imaging and will help capture your favorite nebulas in a totally new light, no matter how polluted your skies may be!\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\u003ca href=\"https:\/\/astronomy-imaging-camera.com\/wp-content\/uploads\/1.25OIII1.jpg\" style=\"background: transparent; color: rgb(238, 57, 57);\"\u003e\u003cimg class=\"alignnone size-large wp-image-4503\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/1.25OIII1-1024x1024_31ffc02d-3294-4750-8239-b456cd576fd8.jpg?v=1766551098\" alt=\"1-25oiii1\" width=\"1024\" height=\"1024\" style=\"border: 0px; max-width: 100%; height: auto; display: block;\"\u003e\u003c\/a\u003e\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\u003cstrong\u003eTechnical Data\u003c\/strong\u003e\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eFWHM 7±0.5nm\u003cbr\u003eThickness 1.9+\/-0.03 mm  (1.25 \/31mm\/36mm)\u003cbr\u003eFine-optically polished to ensure accurate 1\/4 wavefront  over the both surfaces\u003cbr\u003e80% transmission at H-alpha line 656nm (H-Alpha filter )\u003cbr\u003e80% transmission at SII line 672nm (SII filter )\u003cbr\u003e80% transmission at major OIII line 500nm (OIII filter )\u003c\/p\u003e","brand":"ZWO","offers":[{"title":"Default Title","offer_id":44013362053231,"sku":"1.25\" NB set","price":517.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/125-SET11-460x460__02852.jpg?v=1766551100"},{"product_id":"zwo-new-narrowband-36mm-filter","title":"ZWO New narrowband 36mm filter","description":"\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eNarrowband filter do not eliminate the effects of light pollution or increase the object’s brightness. In many cases, they increase the contrast between nebula and night sky, not brightening the nebula.\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eIt can reduce the transmission of certain wavelengths of light, specifically those produced by artificial light including mercury vapor, and both high and low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow).\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\u003cem\u003eForm 2018, ZWO Made a progress on narrowband filters with new standard, provide better performance.\u003c\/em\u003e\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\u003cstrong\u003eTechnical Parameter:\u003c\/strong\u003e\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eName: ZWO New narrowband  36mm filter\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eSize: D=36mm\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eThickness: 2mm\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eThe ZWO  H-Alpha filter  has a bandpass of  7nm and passes light at 656nm  wavelength, light transmission rate comes up to 80%. Best choice of narrowband H-alpha astrophotography filter for high-contrast imaging and revealing rich details of the nebula even in areas with strong light pollution, just prepare to experience the infinite fun with it !\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e \u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/36mm-Ha600_951a6cd8-3860-4669-93e3-0df15616ed9e.jpg?v=1766560378\" style=\"background: transparent; color: rgb(238, 57, 57);\"\u003e\u003cimg class=\"alignnone size-full wp-image-4497\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/36mm-Ha600_951a6cd8-3860-4669-93e3-0df15616ed9e.jpg?v=1766560378\" alt=\"36mm-ha600\" width=\"600\" height=\"600\" style=\"border: 0px; max-width: 100%; height: auto; display: block;\"\u003e\u003c\/a\u003e\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eThe ZWO narrowband S-II 7nm filter passes light at 672nm wavelength with a bandpass of 7nm which is designed for nebula observation . It is suitable for visual observation on most emission nebulae, planetary nebulae and supernova remnants, use it with H-alpha and OIII narrowband filters (SHO Set) for tricolor CCD astrophotography.\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e \u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/36mm-SII600_1ca03eb8-8c2f-4f65-bb3d-088b50cebab6.jpg?v=1766560379\" style=\"background: transparent; color: rgb(238, 57, 57);\"\u003e\u003cimg class=\"alignnone size-full wp-image-4499\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/36mm-SII600_1ca03eb8-8c2f-4f65-bb3d-088b50cebab6.jpg?v=1766560379\" alt=\"36mm-sii600\" width=\"600\" height=\"600\" style=\"border: 0px; max-width: 100%; height: auto; display: block;\"\u003e\u003c\/a\u003e\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eThe ZWO nrrowband O-III 7nm filter is designed for nebula observation allowing 7nm bandwidth of light centered on a wavelength of 500nm through,  which corresponds to OIII emission lines, blocking out all other light.  Adding the ZWO O-III Narrowband filter to your imaging collection will help you go beyond the RGB imaging and will help capture your favorite nebulas in a totally new light, no matter how polluted your skies may be!\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e \u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/36mm-OIII600_8d09ed2b-948c-4aee-b187-52c92060e3ce.jpg?v=1766560381\" style=\"background: transparent; color: rgb(238, 57, 57);\"\u003e\u003cimg class=\"alignnone size-full wp-image-4498\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/36mm-OIII600_8d09ed2b-948c-4aee-b187-52c92060e3ce.jpg?v=1766560381\" alt=\"36mm-oiii600\" width=\"600\" height=\"600\" style=\"border: 0px; max-width: 100%; height: auto; display: block;\"\u003e\u003c\/a\u003e\u003c\/p\u003e\u003cul style=\"margin: 0px 0px 20px 17px; padding: 0px; list-style-position: initial; list-style-image: initial; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\n\u003cli\u003eHubble look of images can be made by the combination of H-alpha, OIII-CCD and SII-CCD, such as the famous “Pillars of Creation” (M16 Eagle Nebula)\u003c\/li\u003e\n\u003cli\u003eNarrowband imaging with SHO set (H-alpha, OIII-CCD and SII-CCD) can be done with the moon up in heavy light pollution, so your equipment is not sitting dormant for several weeks\u003c\/li\u003e\n\u003c\/ul\u003e\u003cul style=\"margin: 0px 0px 20px 17px; padding: 0px; list-style-position: initial; list-style-image: initial; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\u003cli\u003eH-alpha filter is the first narrowband addition to LRGB set for most imagers who blend a black-and-white Ha image into RGB data to enhance structural detail while maintaining natural look\u003c\/li\u003e\u003c\/ul\u003e\u003ch3 style=\"position: relative; padding: 0px 0px 10px; line-height: 28px; color: rgb(238, 57, 57); margin: 0px; font-size: 20px; font-family: \" pt sans narrow sans-serif rgb normal background-color:=\"\" font-weight:=\"\"\u003e\u003c\/h3\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e \u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\u003cstrong\u003eNew OIII filter:\u003c\/strong\u003e\u003c\/p\u003e\u003cp style=\"margin: 0px; zoom: 1; padding: 0px 0px 16px; color: rgb(32, 32, 32); font-family: \" pt sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eBoth side will be fine.\u003c\/p\u003e","brand":"ZWO","offers":[{"title":"Default Title","offer_id":44013713555567,"sku":"ZWO-36mm-NB","price":671.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/new-36mm-SET600-460x460__74283.jpg?v=1766560384"},{"product_id":"zwo-ha-7nm-narrowband-filter","title":"ZWO H-alpha 7nm Narrowband Filter","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe \u003cstrong\u003eZWO H-alpha 7nm Narrowband Filter\u003c\/strong\u003e passes a \u003cstrong\u003e7 nm\u003c\/strong\u003e band centred on the hydrogen-alpha line at \u003cstrong\u003e656 nm\u003c\/strong\u003e and rejects effectively everything else. Peak transmission is around \u003cstrong\u003e90%\u003c\/strong\u003e, off-band rejection is \u003cstrong\u003eOD3 (below 0.1%)\u003c\/strong\u003e, and infrared from \u003cstrong\u003e700–1100 nm is cut\u003c\/strong\u003e. Every size is polished to \u003cstrong\u003e1\/4 wavefront on both surfaces\u003c\/strong\u003e.\u003c\/p\u003e\n\u003cp\u003eAvailable in \u003cstrong\u003ethree sizes — 1.25\" mounted, 36 mm unmounted, and 2\" mounted\u003c\/strong\u003e. Each is a \u003cstrong\u003esingle filter\u003c\/strong\u003e, not a set. Which one you need is decided by your sensor, not your telescope — see the sizing guidance below before ordering.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eChoosing the Right Size\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is the only decision that really matters here, and it is the one most often got wrong. \u003cstrong\u003eA filter too small for your sensor vignettes the corners, and no amount of processing recovers it\u003c\/strong\u003e — the cell wall is a physical obstruction.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" mounted — for sensors up to about 4\/3\":\u003c\/strong\u003e ASI1600, ASI294, ASI533 and similar. Threaded cell, fits 1.25\" filter wheels and any standard 1.25\" thread. 1.9 mm glass. \u003cstrong\u003eWill vignette APS-C and full-frame\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36 mm unmounted — for APS-C and smaller:\u003c\/strong\u003e ASI2600MM, ASI294MM and similar. Bare glass, no cell and no thread, so the full 36 mm is clear aperture. Fits the ZWO 36 mm EFW (7×36 mm). 2 mm glass. \u003cstrong\u003eWill not cover full-frame\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2\" mounted — for sensors up to full-frame:\u003c\/strong\u003e ASI6200MM, ASI2400 and similar. Threaded cell, fits 2\" filter wheels, drawers, and any standard 2\" (M48) thread\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eIf you are between sizes, size up. The cost difference is far smaller than the cost of re-buying.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is a good match if you image \u003cstrong\u003eemission nebulae with a monochrome camera\u003c\/strong\u003e from a light-polluted site. A 7 nm passband rejects mercury vapour, sodium vapour, and atmospheric skyglow almost entirely — which is why narrowband work is productive on nights when broadband imaging is not, including with the Moon up.\u003c\/p\u003e\n\u003cp\u003eIt is also the standard first step \u003cstrong\u003ebeyond LRGB\u003c\/strong\u003e: blending a mono H-alpha channel into RGB data sharpens nebular structure while keeping colour natural. H-alpha is the filter most imagers buy first, because it is where emission nebulae are brightest and where narrowband beats broadband by the widest margin.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e656 nm centre wavelength, 7 nm bandpass:\u003c\/strong\u003e targets the hydrogen-alpha emission line where most nebulae radiate strongest\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFWHM 7 ± 0.5 nm:\u003c\/strong\u003e a tight, specified passband rather than a nominal figure\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApproximately 90% peak transmission\u003c\/strong\u003e at the H-alpha line, with 80% as the floor\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOD3 off-band blocking:\u003c\/strong\u003e under 0.1% transmission outside the passband — this is what kills light pollution\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIR cut from 700–1100 nm:\u003c\/strong\u003e keeps infrared from bloating stars, so no separate UV\/IR-cut filter is needed behind it\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1\/4 wavefront both surfaces:\u003c\/strong\u003e fine-polished, so the filter does not degrade star shapes in a converging beam\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThree sizes:\u003c\/strong\u003e 1.25\" mounted (1.9 mm glass), 36 mm unmounted (2 mm), and 2\" mounted\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eEmission nebulae\u003c\/strong\u003e — Orion, Lagoon, Eagle, North America, Rosette\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary nebulae and supernova remnants\u003c\/strong\u003e — the Ring, Dumbbell, Helix, and the Veil\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSHO \/ Hubble-palette imaging\u003c\/strong\u003e combined with the matching S-II and O-III 7 nm filters\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHa-enhanced LRGB\u003c\/strong\u003e, blending H-alpha into RGB to lift structural detail without shifting colour\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImaging under moonlight or heavy light pollution\u003c\/strong\u003e, where broadband work is not viable\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMonochrome cameras only.\u003c\/strong\u003e A one-shot-colour camera or DSLR has a Bayer matrix, so only the red-sensitive pixels see H-alpha — you lose most of your resolution and most of your light\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36 mm is unmounted:\u003c\/strong\u003e no cell and no thread. It cannot be screwed into a filter drawer or nosepiece — it is retained by M2 screws in a filter wheel recess, and those screws ship with the ZWO 36 mm EFW\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" and 2\" are mounted:\u003c\/strong\u003e threaded cells that fit filter wheels, drawers, and standard filter threads\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThird-party wheels:\u003c\/strong\u003e ZWO specifies filter thickness between 1.5 mm and 3.0 mm for its wheels\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOrientation:\u003c\/strong\u003e ZWO advises that on the current Mark II filters the \u003cstrong\u003ecoated side should face the telescope\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBackfocus:\u003c\/strong\u003e glass in a converging beam shifts focus by roughly one third of its thickness — about 0.6–0.7 mm here. Include it in your 55 mm sum, and use the same thickness in every wheel slot so focus does not shift between channels\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSold singly.\u003c\/strong\u003e For all three channels, the S-II and O-III filters are separate products, or buy the 2\" SHO set\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eImportant Limitations\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot for one-shot-colour cameras or DSLRs.\u003c\/strong\u003e This is a monochrome imaging filter. On a colour sensor the Bayer matrix wastes most of the signal\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSize must match your sensor.\u003c\/strong\u003e 1.25\" vignettes APS-C and full-frame; 36 mm will not cover full-frame. This is a physical obstruction, not a coating issue\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnmounted 36 mm glass must be handled by the edges.\u003c\/strong\u003e There is no cell protecting the coating, and a fingerprint on a narrowband coating is a real problem\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNarrowband does not brighten nebulae — it raises contrast\u003c\/strong\u003e by darkening the sky. Expect longer sub-exposures, not brighter ones\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot a general light-pollution filter.\u003c\/strong\u003e It passes one 7 nm band. Stars and galaxies, which emit broadband, largely disappear\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot for visual observing.\u003c\/strong\u003e A 7 nm H-alpha band is far too dark for the eye\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eA filter wheel and monochrome camera are required\u003c\/strong\u003e and sold separately\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWhich size do I need?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eMatch it to your sensor, not your telescope. Up to about 4\/3\" (ASI1600, ASI294, ASI533), the 1.25\" is fine. APS-C and smaller (ASI2600MM), the 36 mm unmounted. Up to full-frame (ASI6200MM), the 2\". Buying 1.25\" for an APS-C camera vignettes the corners permanently.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is the difference between mounted and unmounted?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA mounted filter sits in a threaded cell you can screw into things. An unmounted filter is bare glass held by screws in a filter wheel. The 36 mm is unmounted precisely because a cell has walls, and walls block the corners of a big sensor.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs this good for beginners?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIt is a sound first narrowband filter if you already have a monochrome camera and a filter wheel. If you image with a one-shot-colour camera, this is not your next purchase — a dual-band filter is.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it work with my ASI2600MC or my DSLR?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNot effectively. Those are colour sensors. Only the red pixels respond to H-alpha, so you throw away roughly three quarters of your resolution. Use a mono camera, or a duo-band filter designed for colour sensors.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhy is my H-alpha image so dark?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThat is the filter working. It rejects over 99.9% of the spectrum. Narrowband raises contrast by darkening the background, not by brightening the target — so plan on longer subs.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I image with the Moon up?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes, and that is much of the point. A 7 nm passband rejects moonlight and light pollution well enough that narrowband nights are the ones a broadband imager writes off.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhich way round does it go?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eZWO advises that on the Mark II filters the coated side should face the telescope.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDo I need a UV\/IR-cut filter as well?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. This filter cuts 700–1100 nm itself, so infrared will not bloat your stars through it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it change my backfocus?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSlightly. Glass shifts focus by roughly a third of its thickness — about 0.6–0.7 mm depending on size. What matters more is using the same thickness across every wheel slot so focus does not jump between channels.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat do I need for the Hubble palette?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eAll three: this H-alpha, plus the S-II 7 nm at 672 nm and the O-III 7 nm at 500 nm. Map them to R, G, and B in processing.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs one filter included, or three?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eOne. Each size option is a single H-alpha filter. The S-II and O-III are separate products.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a 7 nm H-alpha filter at 656 nm with roughly 90% peak transmission, OD3 blocking, and 1\/4 wavefront polish — the first narrowband filter most mono imagers buy, and the one that makes light-polluted and moonlit nights productive. Pick the size from your sensor: 4\/3\" takes 1.25\", APS-C takes 36 mm, full-frame takes 2\".\u003c\/p\u003e","brand":"ZWO","offers":[{"title":"1.25\" mounted","offer_id":53804730679407,"sku":"Ha7nm1.25","price":181.0,"currency_code":"CAD","in_stock":true},{"title":"36mm unmounted","offer_id":53804730712175,"sku":"Ha7nmD36","price":237.0,"currency_code":"CAD","in_stock":true},{"title":"2\" mounted","offer_id":53804730744943,"sku":"Ha7nmD2","price":349.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/08fd46e15c0f7c733a032a761034763d.webp?v=1784084878"},{"product_id":"zwo-sii-7nm-narrowband-filter","title":"ZWO S-II 7nm Narrowband Filter","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe \u003cstrong\u003eZWO S-II 7nm Narrowband Filter\u003c\/strong\u003e passes a \u003cstrong\u003e7 nm\u003c\/strong\u003e band centred on the ionised sulphur line at \u003cstrong\u003e672 nm\u003c\/strong\u003e and rejects effectively everything else. Peak transmission is around \u003cstrong\u003e90%\u003c\/strong\u003e, off-band rejection is \u003cstrong\u003eOD3 (below 0.1%)\u003c\/strong\u003e, and infrared from \u003cstrong\u003e700–1100 nm is cut\u003c\/strong\u003e. Every size is polished to \u003cstrong\u003e1\/4 wavefront on both surfaces\u003c\/strong\u003e.\u003c\/p\u003e\n\u003cp\u003eAvailable in \u003cstrong\u003ethree sizes — 1.25\" mounted, 36 mm unmounted, and 2\" mounted\u003c\/strong\u003e. Each is a \u003cstrong\u003esingle filter\u003c\/strong\u003e, not a set. S-II is the third channel of the SHO trio and the faintest of the three, which matters when you plan integration time.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eChoosing the Right Size\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eSize is decided by your sensor, not your telescope. \u003cstrong\u003eA filter too small vignettes the corners, and no amount of processing recovers it\u003c\/strong\u003e — the cell wall is a physical obstruction.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" mounted — for sensors up to about 4\/3\":\u003c\/strong\u003e ASI1600, ASI294, ASI533 and similar. Threaded cell, 1.9 mm glass. \u003cstrong\u003eWill vignette APS-C and full-frame\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36 mm unmounted — for APS-C and smaller:\u003c\/strong\u003e ASI2600MM, ASI294MM and similar. Bare glass, no cell or thread, so the full 36 mm is clear aperture. Fits the ZWO 36 mm EFW (7×36 mm). 2 mm glass. \u003cstrong\u003eWill not cover full-frame\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2\" mounted — for sensors up to full-frame:\u003c\/strong\u003e ASI6200MM, ASI2400 and similar. Threaded cell, fits 2\" wheels, drawers, and standard M48 threads\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eIf you are between sizes, size up.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is a good match if you are \u003cstrong\u003ealready imaging in H-alpha with a monochrome camera\u003c\/strong\u003e and want to complete the SHO set for Hubble-palette work. S-II sits close to H-alpha in the deep red, but nebulae emit far less strongly in it — so it is a filter you add once the workflow is established, not a starting point.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e672 nm centre wavelength, 7 nm bandpass:\u003c\/strong\u003e targets the ionised sulphur emission line\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFWHM 7 ± 0.5 nm:\u003c\/strong\u003e a tight, specified passband\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApproximately 90% peak transmission\u003c\/strong\u003e at the S-II line\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOD3 off-band blocking:\u003c\/strong\u003e under 0.1% transmission outside the passband\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIR cut from 700–1100 nm:\u003c\/strong\u003e matters more here than on the other channels, since 672 nm sits near the infrared shoulder\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1\/4 wavefront both surfaces:\u003c\/strong\u003e fine-polished, so star shapes are not degraded\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThree sizes:\u003c\/strong\u003e 1.25\" mounted (1.9 mm glass), 36 mm unmounted (2 mm), and 2\" mounted\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSHO \/ Hubble-palette imaging\u003c\/strong\u003e alongside the H-alpha and O-III 7 nm filters\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSupernova remnants\u003c\/strong\u003e — the Veil and similar, where S-II traces shocked gas\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary nebulae\u003c\/strong\u003e, where S-II separates ionisation zones that H-alpha alone blends together\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEmission nebulae\u003c\/strong\u003e where you want the full three-channel palette rather than HOO bicolour\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImaging under moonlight or heavy light pollution\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMonochrome cameras only.\u003c\/strong\u003e On a one-shot-colour sensor the Bayer matrix wastes most of the signal\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36 mm is unmounted:\u003c\/strong\u003e no cell and no thread. It is retained by M2 screws in a filter wheel recess — those screws ship with the ZWO 36 mm EFW\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" and 2\" are mounted:\u003c\/strong\u003e threaded cells that fit filter wheels, drawers, and standard filter threads\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThird-party wheels:\u003c\/strong\u003e ZWO specifies filter thickness between 1.5 mm and 3.0 mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMatch thickness across the wheel\u003c\/strong\u003e so focus does not shift between channels\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOrientation:\u003c\/strong\u003e ZWO advises the \u003cstrong\u003ecoated side should face the telescope\u003c\/strong\u003e on Mark II filters\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBackfocus:\u003c\/strong\u003e glass shifts focus by roughly one third of its thickness — about 0.6–0.7 mm depending on size\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eImportant Limitations\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eS-II is the faintest of the three SHO channels.\u003c\/strong\u003e Expect substantially longer integration than H-alpha for comparable signal. That is astrophysics, not a filter fault\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSize must match your sensor.\u003c\/strong\u003e 1.25\" vignettes APS-C and full-frame; 36 mm will not cover full-frame\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnmounted 36 mm glass must be handled by the edges\u003c\/strong\u003e — no cell protects the coating\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot for one-shot-colour cameras or DSLRs\u003c\/strong\u003e — monochrome imaging only\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot useful on its own.\u003c\/strong\u003e S-II without H-alpha and O-III is one channel of a three-channel palette\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot for visual observing\u003c\/strong\u003e — a 7 nm band at 672 nm is far too dark for the eye\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eA filter wheel and monochrome camera are required\u003c\/strong\u003e and sold separately\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWhy is my S-II data so much weaker than my H-alpha?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eBecause nebulae emit far less strongly at 672 nm than at 656 nm. That is normal and expected. Plan on longer total integration in S-II than in H-alpha — many imagers run roughly twice as long.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhich size do I need?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eMatch it to your sensor, not your telescope. Up to about 4\/3\" (ASI1600, ASI294, ASI533), the 1.25\". APS-C and smaller (ASI2600MM), the 36 mm unmounted. Up to full-frame (ASI6200MM), the 2\".\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is the difference between mounted and unmounted?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA mounted filter sits in a threaded cell you can screw into things. An unmounted filter is bare glass held by screws in a filter wheel. The 36 mm is unmounted because a cell has walls, and walls block the corners of a big sensor.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDo I need this if I already have H-alpha and O-III?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eOnly if you want the full Hubble palette. HOO bicolour from H-alpha and O-III is a perfectly respectable stopping point, and it costs a lot less integration time.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it work with my colour camera or DSLR?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNot effectively. Only the red-sensitive pixels of a Bayer matrix see 672 nm, so you discard most of your resolution and light.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDo I need a UV\/IR-cut filter as well?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. This filter cuts 700–1100 nm itself, which matters for S-II because 672 nm sits close to the infrared.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhich way round does it go?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eZWO advises that on the Mark II filters the coated side should face the telescope.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I image with the Moon up?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes. A 7 nm passband rejects moonlight and light pollution well enough to make those nights productive.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs this good for beginners?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIt is not a first filter. Start with H-alpha, learn the mono narrowband workflow, then add O-III and S-II.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs one filter included, or three?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eOne. Each size option is a single S-II filter.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a 7 nm S-II filter at 672 nm with roughly 90% peak transmission, OD3 blocking, and 1\/4 wavefront polish — the third SHO channel, and the one that needs the most integration time. Pick the size from your sensor: 4\/3\" takes 1.25\", APS-C takes 36 mm, full-frame takes 2\".\u003c\/p\u003e","brand":"ZWO","offers":[{"title":"1.25\" mounted","offer_id":53804739952751,"sku":"SII7nm1.25","price":181.0,"currency_code":"CAD","in_stock":true},{"title":"36mm unmounted","offer_id":53804739985519,"sku":"SII7nmD36","price":237.0,"currency_code":"CAD","in_stock":true},{"title":"2\" mounted","offer_id":53804740018287,"sku":"SII7nmD2","price":349.0,"currency_code":"CAD","in_stock":true}]},{"product_id":"zwo-oiii-7nm-narrowband-filter","title":"ZWO O-III 7nm Narrowband Filter","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe \u003cstrong\u003eZWO O-III 7nm Narrowband Filter\u003c\/strong\u003e passes a \u003cstrong\u003e7 nm\u003c\/strong\u003e band centred on the doubly-ionised oxygen line at \u003cstrong\u003e500 nm\u003c\/strong\u003e and rejects effectively everything else. Peak transmission is around \u003cstrong\u003e90%\u003c\/strong\u003e, off-band rejection is \u003cstrong\u003eOD3 (below 0.1%)\u003c\/strong\u003e, and infrared from \u003cstrong\u003e700–1100 nm is cut\u003c\/strong\u003e. Every size is polished to \u003cstrong\u003e1\/4 wavefront on both surfaces\u003c\/strong\u003e.\u003c\/p\u003e\n\u003cp\u003eAvailable in \u003cstrong\u003ethree sizes — 1.25\" mounted, 36 mm unmounted, and 2\" mounted\u003c\/strong\u003e. Each is a \u003cstrong\u003esingle filter\u003c\/strong\u003e, not a set. O-III sits in the blue-green where most CMOS sensors peak, making it the most efficient of the three SHO channels.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eChoosing the Right Size\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eSize is decided by your sensor, not your telescope. \u003cstrong\u003eA filter too small vignettes the corners, and no amount of processing recovers it\u003c\/strong\u003e — the cell wall is a physical obstruction.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" mounted — for sensors up to about 4\/3\":\u003c\/strong\u003e ASI1600, ASI294, ASI533 and similar. Threaded cell, 1.9 mm glass. \u003cstrong\u003eWill vignette APS-C and full-frame\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36 mm unmounted — for APS-C and smaller:\u003c\/strong\u003e ASI2600MM, ASI294MM and similar. Bare glass, no cell or thread, so the full 36 mm is clear aperture. Fits the ZWO 36 mm EFW (7×36 mm). 2 mm glass. \u003cstrong\u003eWill not cover full-frame\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2\" mounted — for sensors up to full-frame:\u003c\/strong\u003e ASI6200MM, ASI2400 and similar. Threaded cell, fits 2\" wheels, drawers, and standard M48 threads\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eIf you are between sizes, size up.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is a good match if you image \u003cstrong\u003eplanetary nebulae and supernova remnants with a monochrome camera\u003c\/strong\u003e. O-III is where those targets show structure that H-alpha simply does not record — the Veil's filaments and the Helix's inner shell are O-III features.\u003c\/p\u003e\n\u003cp\u003eIt is also the second filter most imagers add after H-alpha, and the partner for HOO bicolour work if you are not ready for the full SHO set.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e500 nm centre wavelength, 7 nm bandpass:\u003c\/strong\u003e targets the major doubly-ionised oxygen emission line\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFWHM 7 ± 0.5 nm:\u003c\/strong\u003e a tight, specified passband\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApproximately 90% peak transmission\u003c\/strong\u003e at the O-III line\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOD3 off-band blocking:\u003c\/strong\u003e rejects mercury and sodium vapour lighting and atmospheric skyglow\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSits near peak sensor QE:\u003c\/strong\u003e back-illuminated CMOS sensors peak in the blue-green, so O-III photons are captured efficiently\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1\/4 wavefront both surfaces:\u003c\/strong\u003e fine-polished, so star shapes are not degraded\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThree sizes:\u003c\/strong\u003e 1.25\" mounted (1.9 mm glass), 36 mm unmounted (2 mm), and 2\" mounted\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary nebulae\u003c\/strong\u003e — the Ring, Dumbbell, and Helix, where O-III carries the inner structure\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSupernova remnants\u003c\/strong\u003e — the Veil, whose filamentary detail is largely an O-III signal\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHOO bicolour imaging\u003c\/strong\u003e, mapping H-alpha to red and O-III to green and blue\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSHO \/ Hubble-palette imaging\u003c\/strong\u003e alongside the H-alpha and S-II 7 nm filters\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImaging under moonlight or heavy light pollution\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMonochrome cameras only.\u003c\/strong\u003e On a one-shot-colour sensor the Bayer matrix wastes most of the signal\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36 mm is unmounted:\u003c\/strong\u003e no cell and no thread. It is retained by M2 screws in a filter wheel recess — those screws ship with the ZWO 36 mm EFW\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25\" and 2\" are mounted:\u003c\/strong\u003e threaded cells that fit filter wheels, drawers, and standard filter threads\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFast optics shift narrowband passbands.\u003c\/strong\u003e Below roughly f\/4 the steep cone angle blue-shifts the effective centre wavelength of any narrowband filter — O-III is the channel where that shows first\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThird-party wheels:\u003c\/strong\u003e ZWO specifies filter thickness between 1.5 mm and 3.0 mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMatch thickness across the wheel\u003c\/strong\u003e so focus does not shift between channels\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOrientation:\u003c\/strong\u003e ZWO advises the \u003cstrong\u003ecoated side should face the telescope\u003c\/strong\u003e on Mark II filters\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eImportant Limitations\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot for visual observing.\u003c\/strong\u003e A 7 nm imaging filter is far darker than the visual O-III filters sold for eyepiece use — do not confuse the two\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSize must match your sensor.\u003c\/strong\u003e 1.25\" vignettes APS-C and full-frame; 36 mm will not cover full-frame\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHalos around bright stars are the classic O-III complaint.\u003c\/strong\u003e ZWO's Mark II filters improved this, but any narrowband filter can halo on a very bright star in the field. Framing helps more than processing\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnmounted 36 mm glass must be handled by the edges\u003c\/strong\u003e — no cell protects the coating\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot for one-shot-colour cameras or DSLRs\u003c\/strong\u003e — monochrome imaging only\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNarrowband raises contrast, not brightness.\u003c\/strong\u003e Expect long sub-exposures\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eA filter wheel and monochrome camera are required\u003c\/strong\u003e and sold separately\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eIs this the same as a visual O-III filter?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo, and this is a common and expensive mix-up. Visual O-III filters for eyepiece use run much wider passbands so there is enough light to see. A 7 nm imaging filter is far too dark for the eye. Buy the visual version if you observe.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhich size do I need?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eMatch it to your sensor, not your telescope. Up to about 4\/3\" (ASI1600, ASI294, ASI533), the 1.25\". APS-C and smaller (ASI2600MM), the 36 mm unmounted. Up to full-frame (ASI6200MM), the 2\".\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is the difference between mounted and unmounted?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA mounted filter sits in a threaded cell you can screw into things. An unmounted filter is bare glass held by screws in a filter wheel. The 36 mm is unmounted because a cell has walls, and walls block the corners of a big sensor.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhich do I buy after H-alpha?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eO-III, usually. It gives you HOO bicolour immediately, and it records structure in planetary nebulae and supernova remnants that H-alpha misses entirely.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhy do I get halos around bright stars?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIt is the classic narrowband O-III artefact. ZWO's Mark II filters reduced it, but a very bright star in the field can still halo. Reframing to move the star out is more effective than trying to fix it later.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill this work at f\/3?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eWith a caveat. Below about f\/4 the steep light cone shifts a narrowband filter's effective centre wavelength blueward, and O-III is where you notice it first — transmission at the true line drops. It still works; it just works less well than at f\/5 or slower.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it work with my colour camera or DSLR?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNot effectively. Only some pixels of a Bayer matrix see 500 nm, so you discard most of your resolution and light.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhich way round does it go?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eZWO advises that on the Mark II filters the coated side should face the telescope.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I image with the Moon up?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes. A 7 nm passband rejects moonlight well enough to make those nights productive.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs one filter included, or three?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eOne. Each size option is a single O-III filter.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a 7 nm O-III filter at 500 nm with roughly 90% peak transmission, OD3 blocking, and 1\/4 wavefront polish — the second narrowband filter most mono imagers buy, and the channel that carries planetary nebulae and supernova remnants. Not a visual O-III filter. Pick the size from your sensor: 4\/3\" takes 1.25\", APS-C takes 36 mm, full-frame takes 2\".\u003c\/p\u003e","brand":"ZWO","offers":[{"title":"1.25\" mounted","offer_id":53804748701807,"sku":"OIII7nm1.25","price":181.0,"currency_code":"CAD","in_stock":true},{"title":"36mm unmounted","offer_id":53804748734575,"sku":"OIII7nmD36","price":237.0,"currency_code":"CAD","in_stock":true},{"title":"2\" mounted","offer_id":53804748767343,"sku":"OIII7nmD2","price":349.0,"currency_code":"CAD","in_stock":true}]}],"url":"https:\/\/ontariotelescope.com\/collections\/zwo-narrowband.oembed","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}