{"product_id":"svbony-sv220-1-25-3nm-h-alpha-oiii-dual-band-filter-w9198a","title":"SVBONY SV220 1.25″ 3nm H-Alpha \u0026 OIII Dual-Band Filter (W9198A)","description":"\u003cstyle\u003e\n.dcs-sv220{max-width:940px;margin:0 auto;color:#28394e;font-size:16px;line-height:1.7;overflow-wrap:break-word}\n.dcs-sv220 *{box-sizing:border-box}\n.dcs-sv220 p{font-size:16px;line-height:1.7;margin:0 0 16px}\n.dcs-sv220 h2{color:#10243d;font-size:27px;line-height:1.25;letter-spacing:-.3px;margin:0 0 16px;text-transform:none}\n.dcs-sv220 h3{color:#10243d;font-size:19px;line-height:1.4;margin:0 0 10px;text-transform:none}\n.dcs-sv220 a{color:#1c5579;text-underline-offset:3px}\n.dcs-sv220 a:focus-visible,.dcs-sv220 summary:focus-visible{outline:3px solid #ce941f;outline-offset:4px}\n.dcs-sv220 .dcs-hero{background:#10243d;color:#fff;border-top:5px solid #e8b641;border-radius:14px;padding:28px;margin:0 0 18px}\n.dcs-sv220 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th{width:30%}\n.dcs-sv220 .dcs-small{font-size:13px;line-height:1.6;color:#52647a}\n.dcs-sv220 .dcs-steps{padding-left:24px;margin:18px 0}\n.dcs-sv220 .dcs-steps li{padding-left:4px;margin:0 0 14px;font-size:15px;line-height:1.7}\n.dcs-sv220 details{border-bottom:1px solid #dce4ec;padding:0;background:none}\n.dcs-sv220 summary{display:list-item;cursor:pointer;padding:16px 4px;font-size:16px;font-weight:600;line-height:1.5;color:#163550}\n.dcs-sv220 details p{font-size:15px;padding:0 4px 6px}\n.dcs-sv220 .dcs-cta{background:#10243d;color:#e7eef5;padding:27px;border-radius:12px;margin-top:35px}\n.dcs-sv220 .dcs-cta h2{color:#fff;font-size:25px}\n.dcs-sv220 .dcs-button{display:inline-block;background:#efc45f;color:#10243d!important;border-radius:7px;padding:12px 18px;text-decoration:none;font-weight:700;margin:4px 0 17px;font-size:14px}\n.dcs-sv220 .dcs-related{font-size:14px;line-height:1.8;margin:0}\n.dcs-sv220 .dcs-cta .dcs-related a{color:#fff}\n.dcs-sv220 .dcs-brandline{font-size:12px;color:#e8c46c;margin-top:17px;padding-top:17px;border-top:1px solid #34516c}\n@media(max-width:600px){\n .dcs-sv220 p{font-size:15px}\n .dcs-sv220 h2{font-size:24px}\n .dcs-sv220 .dcs-hero,.dcs-sv220 .dcs-cta{padding:23px 20px}\n .dcs-sv220 .dcs-stats{grid-template-columns:repeat(2,minmax(0,1fr))}\n .dcs-sv220 .dcs-two{gap:20px}\n .dcs-sv220 .dcs-two\u003e*{flex-basis:100%}\n .dcs-sv220 th,.dcs-sv220 td{padding:10px;font-size:13px}\n}\n\u003c\/style\u003e\u003cdiv class=\"dcs-sv220\"\u003e\n\u003csection class=\"dcs-hero\"\u003e\u003cp class=\"dcs-eyebrow\"\u003eDark Clear Skies · SVBONY SV220 · W9198A\u003c\/p\u003e\n\u003ch2\u003eSV220 3nm H-alpha \u0026amp; OIII\u003c\/h2\u003e\n\u003cp class=\"dcs-subtitle\"\u003eNarrowband nebula imaging in a compact fitting.\u003c\/p\u003e\n\u003cp\u003eCapture two nebula emission bands during the same exposure while rejecting much of the surrounding sky background. This is the 1.25-inch mounted version, W9198A.\u003c\/p\u003e\u003c\/section\u003e\u003cdiv class=\"dcs-stats\" aria-label=\"Key filter specifications\"\u003e\n\u003cdiv class=\"dcs-stat\"\u003e\n\u003cstrong\u003e3nm\u003c\/strong\u003e\u003cspan\u003eNominal bandwidth per band\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"dcs-stat\"\u003e\n\u003cstrong\u003e1.25″\u003c\/strong\u003e\u003cspan\u003eMounted filter format\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"dcs-stat\"\u003e\n\u003cstrong\u003e26mm\u003c\/strong\u003e\u003cspan\u003eClear aperture\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"dcs-stat\"\u003e\n\u003cstrong\u003eHα + OIII\u003c\/strong\u003e\u003cspan\u003eTwo emission bands\u003c\/span\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cp\u003eThe \u003cstrong\u003eSVBONY SV220 W9198A\u003c\/strong\u003e combines nominal 3nm H-alpha and OIII transmission windows in a \u003cstrong\u003e1.25-inch mounted filter\u003c\/strong\u003e. Its 26mm clear aperture and M28.5 × 0.6 male thread suit imaging trains designed around this compact format, provided the opening and cell clearance match your equipment.\u003c\/p\u003e\n\u003cfigure class=\"dcs-product-photo\"\u003e\u003cdiv class=\"dcs-photo\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1_20260209103830_3399.webp?v=1794052397\" aria-label=\"Open larger image: SVBONY SV220 1.25-inch 3nm H-alpha and OIII filter W9198A\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1_20260209103830_3399.webp?v=1794052397\" alt=\"SVBONY SV220 1.25-inch 3nm H-alpha and OIII filter W9198A\" width=\"1200\" height=\"1200\" loading=\"lazy\" decoding=\"async\"\u003e\u003c\/a\u003e\u003c\/div\u003e\n\u003cfigcaption\u003eThe W9198A is a single mounted dual-band imaging filter. Check the size and SKU when comparing the SV220 range.\u003c\/figcaption\u003e\u003c\/figure\u003e\u003cul class=\"dcs-benefits\"\u003e\n\u003cli\u003e\n\u003cstrong\u003eBoth emission bands together.\u003c\/strong\u003e Record hydrogen-alpha at 656.3nm and oxygen-III at 500.7nm during the same exposure.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNarrow windows for nebula contrast.\u003c\/strong\u003e Nominal 3nm passbands reject much of the nearby spectrum; the specified FWHM tolerance is 3 ± 1nm for each band.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDefined mechanical fit.\u003c\/strong\u003e A 26mm clear aperture, M28.5 × 0.6 male thread and 7mm-high cell let you check your holder before ordering.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003csection class=\"dcs-section\"\u003e\u003ch2 class=\"dcs-section-heading\"\u003eWhat the 3nm design helps you capture\u003c\/h2\u003e\n\u003cp\u003eNarrowband imaging selects the wavelengths emitted by glowing gas. The SV220 passes two useful emission regions and blocks much of the unwanted light around them, helping faint nebular structure stand out from the sky background.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eFWHM\u003c\/strong\u003e means full width at half maximum: the width of each transmission band measured at half its peak transmission. The quoted 3nm describes a nominal bandwidth, not the thickness of the glass; SVBONY specifies \u003cstrong\u003e3 ± 1nm per passband\u003c\/strong\u003e and a \u003cstrong\u003e2.0mm substrate\u003c\/strong\u003e.\u003c\/p\u003e\n\u003cfigure class=\"\"\u003e\u003cdiv class=\"dcs-photo\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/w9198a-2_20250901175826_2447.jpg?v=1794052397\" aria-label=\"Open larger image: SVBONY SV220 3nm transmission graph showing OIII and H-alpha passbands across 300 to 1050nm\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/w9198a-2_20250901175826_2447.jpg?v=1794052397\" alt=\"SVBONY SV220 3nm transmission graph showing OIII and H-alpha passbands across 300 to 1050nm\" width=\"1200\" height=\"1200\" loading=\"lazy\" decoding=\"async\"\u003e\u003c\/a\u003e\u003c\/div\u003e\n\u003cfigcaption\u003eSVBONY’s 3nm H-alpha\/OIII transmission illustration. The two narrow peaks are the intended passbands; the surrounding spectrum is strongly suppressed. Manufacturer illustration, not a test certificate for an individual filter. Select it to inspect the graph.\u003c\/figcaption\u003e\u003c\/figure\u003e\u003cp\u003eSVBONY rates the OIII\/H-alpha average peak transmission at \u003cstrong\u003e≥85%\u003c\/strong\u003e, with \u003cstrong\u003eaverage OD5 out-of-band blocking\u003c\/strong\u003e across its specified 300–1050nm blocking range. These ratings describe the filter; the final image also depends on the telescope, sensor, sky and capture technique.\u003c\/p\u003e\u003c\/section\u003e\u003csection class=\"dcs-section\"\u003e\u003ch2 class=\"dcs-section-heading\"\u003eA specialist filter for emission nebulae\u003c\/h2\u003e\n\u003cdiv class=\"dcs-two\"\u003e\n\u003cdiv class=\"dcs-card\"\u003e\n\u003ch3\u003eChoose emission-rich targets\u003c\/h3\u003e\n\u003cp\u003eThe SV220 suits \u003cstrong\u003eemission nebulae, planetary nebulae and supernova remnants\u003c\/strong\u003e that emit H-alpha and\/or OIII light. Subjects such as the North America Nebula, the Veil complex and the Dumbbell Nebula give these passbands useful work to do.\u003c\/p\u003e\n\u003cp\u003eThe balance of red hydrogen and blue-green oxygen varies from object to object, so different targets will respond differently.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"dcs-card\"\u003e\n\u003ch3\u003ePlan a broadband approach for other subjects\u003c\/h3\u003e\n\u003cp\u003eGalaxies, reflection nebulae and star clusters emit much of their light across a broad spectrum. A narrow dual-band filter rejects a large part of that light, so it is not a general-purpose filter to leave in place for every target.\u003c\/p\u003e\n\u003cp\u003eYou can still collect separate narrowband data to emphasise emission regions in a galaxy, then combine it with suitable broadband imaging.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"dcs-note\"\u003e\n\u003ch3\u003eMoonlight and city skies still matter\u003c\/h3\u003e\n\u003cp\u003eThe narrow passbands can help with unwanted background light, but they do not make a bright moonlit sky equivalent to a dark site. Choose a suitable target and plan enough total integration time.\u003c\/p\u003e\n\u003c\/div\u003e\u003c\/section\u003e\u003csection class=\"dcs-section\"\u003e\u003ch2 class=\"dcs-section-heading\"\u003eCheck the thread, holder and sensor coverage\u003c\/h2\u003e\n\u003cp\u003eThis version has a \u003cstrong\u003esingle external M28.5 × 0.6 thread\u003c\/strong\u003e. Use a drawer, wheel or holder intended for a 1.25-inch mounted filter, and allow clearance for the \u003cstrong\u003eØ31.75 × 7mm cell\u003c\/strong\u003e. A camera’s M42 or M48 connection alone does not establish which filter cell its holder accepts.\u003c\/p\u003e\n\u003cp\u003eThe 26mm clear aperture needs checking against the sensor dimensions, filter-to-sensor distance and working focal ratio. It can suit compact imaging trains, but do not assume it will illuminate the corners of a larger sensor in every arrangement.\u003c\/p\u003e\n\u003cdiv class=\"dcs-note\"\u003e\n\u003ch3\u003eCheck the whole light path\u003c\/h3\u003e\n\u003cp\u003eA narrow adapter or holder can restrict the field even when the filter itself is large enough. Check all openings between the telescope and sensor, and follow the optical system’s back-focus guidance.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cfigure class=\"\"\u003e\u003cdiv class=\"dcs-photo\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/w9198a-8_20250901175840_8690.jpg?v=1794229514\" aria-label=\"Open larger image: SVBONY W9198A dimensions showing a 31.75mm diameter cell, 7mm height and M28.5 by 0.6 thread\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/w9198a-8_20250901175840_8690.jpg?v=1794229514\" alt=\"SVBONY W9198A dimensions showing a 31.75mm diameter cell, 7mm height and M28.5 by 0.6 thread\" width=\"1200\" height=\"1200\" loading=\"lazy\" decoding=\"async\"\u003e\u003c\/a\u003e\u003c\/div\u003e\n\u003cfigcaption\u003eManufacturer’s W9198A dimension drawing. Use the 7mm cell height to check wheel or drawer clearance; the 26mm clear aperture is listed separately in the specifications.\u003c\/figcaption\u003e\u003c\/figure\u003e\u003cp\u003eNeed a larger clear opening? Compare the \u003ca href=\"https:\/\/www.darkclearskies.co.uk\/products\/svbony-sv220-2-inch-3nm-narrowband-filter\"\u003e2-inch SV220 3nm W9198B\u003c\/a\u003e, subject to the holder and optical geometry of your system.\u003c\/p\u003e\u003c\/section\u003e\u003csection class=\"dcs-section\"\u003e\u003ch2 class=\"dcs-section-heading\"\u003eMatch the filter to your camera and focal ratio\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eOne-shot-colour astronomy cameras:\u003c\/strong\u003e both emission bands reach the sensor during the same exposure. With suitable processing, the red and blue\/green channel information can be used for an H-alpha\/OIII nebula image or an HOO-style colour combination.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eMonochrome cameras:\u003c\/strong\u003e the filter passes both bands together, so one exposure combines their light into a greyscale image. Use individual narrowband filters when you need separately controlled H-alpha and OIII datasets.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDSLR and mirrorless cameras:\u003c\/strong\u003e check the mounting arrangement and your camera’s H-alpha sensitivity. A camera’s internal filter can reduce the red nebula signal; an external SV220 cannot restore light already rejected inside the camera.\u003c\/p\u003e\n\u003cdiv class=\"dcs-note dcs-note-gold\"\u003e\n\u003ch3\u003eFast optics need a specific compatibility check\u003c\/h3\u003e\n\u003cp\u003eThe 3nm windows are sensitive to the angle of the incoming light. A fast telescope or focal reducer can shift the transmission bands and reduce useful H-alpha or OIII throughput. Ask us to check systems working at \u003cstrong\u003ef\/5 or faster\u003c\/strong\u003e; do not assume this standard filter is suitable for an f\/2 RASA or HyperStar configuration.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cp\u003eA physical fit and an optical match are separate checks. The telescope’s \u003cstrong\u003eworking focal ratio with its reducer installed\u003c\/strong\u003e is the figure to use when discussing suitability.\u003c\/p\u003e\u003c\/section\u003e\u003csection class=\"dcs-section\"\u003e\u003ch2 class=\"dcs-section-heading\"\u003eSV220 7nm or 3nm: which should you choose?\u003c\/h2\u003e\n\u003cp\u003eBoth versions record H-alpha and OIII. The difference is the width of the transmission windows around those emission lines.\u003c\/p\u003e\n\u003cdiv class=\"dcs-table-wrap\"\u003e\u003ctable class=\"dcs-compare\"\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth scope=\"col\"\u003eBuying consideration\u003c\/th\u003e\n\u003cth scope=\"col\"\u003eSV220 7nm\u003c\/th\u003e\n\u003cth scope=\"col\"\u003eSV220 3nm\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eBandwidth per emission band\u003c\/th\u003e\n\u003ctd\u003e7nm FWHM\u003c\/td\u003e\n\u003ctd\u003eNominal 3nm; specified 3 ± 1nm FWHM\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eMain reason to choose it\u003c\/th\u003e\n\u003ctd\u003eA broader passband and an accessible route into dual-band nebula imaging.\u003c\/td\u003e\n\u003ctd\u003eNarrower windows to reject more surrounding sky background, when matched to the optical system.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eFast telescope check\u003c\/th\u003e\n\u003ctd\u003eRequired: this is not a dedicated high-speed filter.\u003c\/td\u003e\n\u003ctd\u003eEspecially important because the narrower bands are sensitive to optical band shift.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003c\/div\u003e\n\u003cp\u003eA narrower bandwidth does not automatically mean shorter exposures or a better result in every setup. Telescope speed, filter transmission, sky brightness, target emission and processing all contribute.\u003c\/p\u003e\n\u003cp class=\"dcs-small\"\u003eSee the \u003ca href=\"https:\/\/www.darkclearskies.co.uk\/products\/sv220-telescope-filter-7nm-dual-band-nebula-2\"\u003eSV220 7nm filter in both sizes\u003c\/a\u003e for the broader-band option.\u003c\/p\u003e\u003c\/section\u003e\u003csection class=\"dcs-section\"\u003e\u003ch2 class=\"dcs-section-heading\"\u003eSet up and capture with confidence\u003c\/h2\u003e\n\u003col class=\"dcs-steps\"\u003e\n\u003cli\u003e\n\u003cstrong\u003eConfirm the mechanical fit.\u003c\/strong\u003e Match the filter thread and cell clearance to the holder. The nominal filter size is not the camera connection thread.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCheck the complete optical train.\u003c\/strong\u003e Include any reducer when checking focal ratio, and follow the telescope or flattener manufacturer’s back-focus guidance. Filter glass thickness and holder length are different measurements.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRefocus with the filter installed.\u003c\/strong\u003e Use a test frame to check focus, background level, bright-star saturation and illumination across the sensor.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCalibrate consistently.\u003c\/strong\u003e Capture suitable flat frames with the same filter and optical arrangement used for your light frames. Build total integration time around the target and conditions.\u003c\/li\u003e\n\u003c\/ol\u003e\u003c\/section\u003e\u003csection class=\"dcs-section\"\u003e\u003ch2 class=\"dcs-section-heading\"\u003eTechnical specifications\u003c\/h2\u003e\n\u003cdiv class=\"dcs-table-wrap\"\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth scope=\"col\"\u003eSpecification\u003c\/th\u003e\n\u003cth scope=\"col\"\u003eW9198A · 1.25″ · 3nm\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eBrand \/ model \/ SKU\u003c\/th\u003e\n\u003ctd\u003eSVBONY \/ SV220 \/ W9198A\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eMounted format\u003c\/th\u003e\n\u003ctd\u003e1.25-inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eFilter type\u003c\/th\u003e\n\u003ctd\u003eDual-band H-alpha and OIII imaging filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eNominal centre wavelengths\u003c\/th\u003e\n\u003ctd\u003eOIII 500.7nm; H-alpha 656.3nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eFWHM bandwidth\u003c\/th\u003e\n\u003ctd\u003eOIII 3 ± 1nm; H-alpha 3 ± 1nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003ePeak transmission\u003c\/th\u003e\n\u003ctd\u003eOIII\/H-alpha average ≥85%\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eSpecified blocking range\u003c\/th\u003e\n\u003ctd\u003e300–1050nm, outside the intended transmission windows\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eOut-of-band blocking\u003c\/th\u003e\n\u003ctd\u003eAverage OD5\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eClear aperture\u003c\/th\u003e\n\u003ctd\u003e26mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eMounting thread\u003c\/th\u003e\n\u003ctd\u003eM28.5 × 0.6; single male thread\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eCell diameter × height\u003c\/th\u003e\n\u003ctd\u003eØ31.75 × 7mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eSubstrate thickness\u003c\/th\u003e\n\u003ctd\u003e2.0mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eCell material\u003c\/th\u003e\n\u003ctd\u003e6061T aluminium\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eSurface quality\u003c\/th\u003e\n\u003ctd\u003e60\/40\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eParallelism\u003c\/th\u003e\n\u003ctd\u003e30 arcseconds\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eManufacturer-listed net weight\u003c\/th\u003e\n\u003ctd\u003e7g\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003c\/div\u003e\n\u003cp\u003eOptical ratings and dimensions are manufacturer specifications. Substrate thickness is the glass thickness; it is different from cell height and from the optical length of a complete filter holder.\u003c\/p\u003e\u003c\/section\u003e\u003csection class=\"dcs-section\"\u003e\u003ch2 class=\"dcs-section-heading\"\u003eWhat is included?\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eOne SVBONY SV220 1.25-inch mounted 3nm H-alpha\/OIII filter (W9198A).\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe telescope, camera, filter drawer or wheel, adapters and any additional filters are separate items. Equipment shown in manufacturer compatibility illustrations is not included with this filter.\u003c\/p\u003e\u003c\/section\u003e\u003csection class=\"dcs-section\"\u003e\u003ch2 class=\"dcs-section-heading\"\u003ePractical questions before you buy\u003c\/h2\u003e\n\u003cdetails\u003e\u003csummary\u003eCan I use it under a bright Moon?\u003c\/summary\u003e\u003cp\u003eIt can help separate nebula emission from unwanted background light, but moonlit conditions still affect the result. Keep your expectations, target choice and total integration time appropriate to the sky. A darker sky remains useful.\u003c\/p\u003e\u003c\/details\u003e\u003cdetails\u003e\u003csummary\u003eDoes one filter give me a complete SHO image?\u003c\/summary\u003e\u003cp\u003eThis filter records H-alpha and OIII. A three-channel SHO dataset also needs independently captured SII information. HOO typically maps H-alpha to red and OIII to green and blue. SHO maps SII, H-alpha and OIII to those three channels respectively, so it requires additional sulphur data.\u003c\/p\u003e\u003c\/details\u003e\u003cdetails\u003e\u003csummary\u003eWhat exposure time should I use?\u003c\/summary\u003e\u003cp\u003eThere is no universal exposure time. Start with settings appropriate to your camera and telescope, inspect a test frame, and adjust for background level, star saturation and tracking. Total integration time matters as well as the length of each exposure.\u003c\/p\u003e\u003c\/details\u003e\u003cdetails\u003e\u003csummary\u003eWill every bright star be free from halos?\u003c\/summary\u003e\u003cp\u003eHalos and reflections depend on the filter, bright star, camera window and the rest of the optical train. Results vary between imaging systems, so halo-free performance cannot be guaranteed.\u003c\/p\u003e\u003c\/details\u003e\u003cdetails\u003e\u003csummary\u003eIs this intended for visual observing or the Sun?\u003c\/summary\u003e\u003cp\u003eThe SV220 is an astrophotography filter. It is not a solar filter and must never be used as solar protection.\u003c\/p\u003e\u003c\/details\u003e\u003c\/section\u003e\u003csection class=\"dcs-cta\"\u003e\u003ch2\u003eChoose a filter that fits your imaging setup\u003c\/h2\u003e\n\u003cp\u003eTell us your camera, telescope, reducer and filter holder. Dark Clear Skies can help you check the size, thread and working focal ratio before you order.\u003c\/p\u003e\n\u003ca class=\"dcs-button\" href=\"https:\/\/www.darkclearskies.co.uk\/pages\/contact\"\u003eAsk DCS about compatibility\u003c\/a\u003e\u003cp class=\"dcs-related\"\u003e\u003ca href=\"https:\/\/www.darkclearskies.co.uk\/products\/sv220-telescope-filter-7nm-dual-band-nebula-2\"\u003eSV220 7nm · both sizes\u003c\/a\u003e · \u003ca href=\"https:\/\/www.darkclearskies.co.uk\/products\/svbony-sv220-2-inch-3nm-narrowband-filter\"\u003eSV220 3nm · 2-inch\u003c\/a\u003e\u003cbr\u003e\u003ca href=\"https:\/\/www.darkclearskies.co.uk\/collections\/svbony-telescope-filters\"\u003eExplore SVBONY telescope filters\u003c\/a\u003e\u003c\/p\u003e\n\u003cdiv class=\"dcs-brandline\"\u003eDark Clear Skies · Passion for the Night Sky, Delivered.\u003c\/div\u003e\u003c\/section\u003e\n\u003c\/div\u003e","brand":"SVBONY","offers":[{"title":"Default Title","offer_id":55729304469880,"sku":"W9198A","price":135.0,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1_20260209103830_3399.webp?v=1794052397","url":"https:\/\/www.darkclearskies.co.uk\/products\/svbony-sv220-1-25-3nm-h-alpha-oiii-dual-band-filter-w9198a","provider":"Dark Clear Skies ","version":"1.0","type":"link"}