{"product_id":"svbony-sv115-1-25-oiii-18nm-filter","title":"SVBONY SV115 1.25″ OIII 18nm Narrowband Filter","description":"\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/1_20250806114205_1998_20260810140508_1030.webp?v=1791670161\" alt=\"SVBONY SV115 1.25″ OIII 18nm filter\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe SVBONY SV115 1.25″ (item F9186A) is an O-III narrowband filter with an 18 ± 2 nm passband. It transmits 90% at the 495.9 nm and 500.7 nm doubly-ionized oxygen lines and blocks across 400–700 nm, using dichroic interference and anti-reflection coatings on 1.85 mm glass. It threads into any 1.25″ eyepiece or diagonal.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThis is a good match if you observe emission and planetary nebulae visually and want more contrast between the nebula and the sky background, including on bright targets such as M42 from light-polluted locations.\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/2_20250806114205_1676.jpg?v=1791670162\" alt=\"SVBONY SV115 1.25″ OIII filter\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e18 ± 2 nm FWHM:\u003c\/strong\u003e centred on the O-III emission lines.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e90% transmission\u003c\/strong\u003e at 495.9 nm and 500.7 nm.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e400–700 nm blocking:\u003c\/strong\u003e suppresses the rest of the visible spectrum.\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eDichroic interference and anti-reflection coatings.\u003c\/strong\u003e\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.85 mm glass\u003c\/strong\u003e in a standard 1.25″ cell.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eOptical Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003ePlanetary nebulae and many emission nebulae radiate strongly in the two O-III lines near 500 nm. By passing an 18 nm band around them and blocking the rest, the filter darkens the sky background far more than the nebula, so the object stands out. It increases contrast rather than brightness, which is why SVBONY recommends larger apertures under dark, clear skies with good seeing for the best results.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary nebulae\u003c\/strong\u003e such as the Ring and Dumbbell.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEmission nebulae\u003c\/strong\u003e with strong O-III emission.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBright nebulae like M42\u003c\/strong\u003e under light pollution.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/3_20250806114205_1996.jpg?v=1791670162\" alt=\"SVBONY SV115 1.25″ OIII filter cell\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSize:\u003c\/strong\u003e 1.25″, threads into 1.25″ eyepieces and diagonals.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2″ version:\u003c\/strong\u003e SVBONY also makes the SV115 in 2″ as a separate product.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eContrast, not brightness:\u003c\/strong\u003e the filter dims stars and sky along with blocking light pollution; the nebula stands out because the background darkens more.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNarrowband target list:\u003c\/strong\u003e it suits O-III-rich nebulae; galaxies and star clusters do not benefit.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e SVBONY does not publish a weight for this filter.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eNo. Thread it onto the bottom of a 1.25″ eyepiece or into a diagonal's nosepiece.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill it remove light pollution?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eIt does not remove light pollution, but it increases the contrast between O-III nebulae and the sky.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhich telescope works best?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eSVBONY recommends a large-aperture telescope under clear, dark skies with good seeing.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eIn short: a 1.25″ 18 nm O-III filter with 90% line transmission and 400–700 nm blocking, for higher-contrast views of planetary and emission nebulae.\u003c\/p\u003e","brand":"SvBony","offers":[{"title":"Default Title","offer_id":67722237182063,"sku":"F9186A","price":65.54,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/1_20250806114205_1998_20260810140508_1030.webp?v=1791670161","url":"https:\/\/ontariotelescope.com\/products\/svbony-sv115-1-25-oiii-18nm-filter","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}