{"product_id":"svbony-sv135-7-21mm-zoom-eyepiece-52-36","title":"SVBONY SV135 1.25″ 7–21mm 52°–36° Zoom Eyepiece","description":"\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6387599306152461862670958.jpg?v=1791669868\" alt=\"SVBONY SV135 7-21mm 52-36 degree zoom eyepiece key visual\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe SVBONY SV135 52°–36° is a 1.25″ zoom eyepiece that changes focal length from 7 mm to 21 mm with a twist of the barrel, so one eyepiece covers the range of several fixed ones. It uses five elements in three groups of high-index glass, fully multi-coated, with an apparent field of 52° at 7 mm narrowing to 36° at 21 mm and 13–14 mm of eye relief. It weighs 95 g and has an M28.5 × 0.6 filter thread.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThis is a good match if you want one light eyepiece to move between magnifications on the Moon, Jupiter and Saturn, matching the power to the seeing without stopping to swap eyepieces.\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6387599306187768105565964.jpg?v=1791669868\" alt=\"SVBONY SV135 7-21mm zoom eyepiece for planetary and lunar viewing\" 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\u003e7–21 mm linear zoom:\u003c\/strong\u003e continuous magnification change.\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003e52°–36° apparent field.\u003c\/strong\u003e\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e13–14 mm eye relief:\u003c\/strong\u003e with a rubber eyecup for use with or without glasses.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFully multi-coated, 3 groups \/ 5 elements\u003c\/strong\u003e of high-index glass.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSafety undercut on the barrel:\u003c\/strong\u003e helps keep it from slipping out of the focuser or diagonal.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBlackened lens edges and anti-reflection threads:\u003c\/strong\u003e for contrast.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6387599306223869997504390.jpg?v=1791669869\" alt=\"SVBONY SV135 7-21mm zoom eyepiece design details\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eOptical Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eAs a linear zoom, the SV135 changes focal length in proportion to barrel rotation. Its five elements in three groups give a 52° field at 7 mm and 36° at 21 mm — the narrowing field at longer focal lengths is typical of zoom designs. On a 1000 mm telescope the range works out to roughly 48× to 143×.\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/w9105b-2_20250807161536_5542.jpg?v=1791670292\" alt=\"SVBONY SV135 7-21mm zoom eyepiece with rubber eye guard\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanets:\u003c\/strong\u003e Jupiter, Saturn and Mars, zooming to match the seeing.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMoon:\u003c\/strong\u003e whole-disc to close-up crater views.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStar clusters and nebulae\u003c\/strong\u003e at the lower-power end.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary photography:\u003c\/strong\u003e SVBONY also lists it for simple planetary imaging through the eyepiece.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eBarrel:\u003c\/strong\u003e 1.25″, for standard 1.25″ focusers and diagonals.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilters:\u003c\/strong\u003e M28.5 × 0.6 thread.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOther SV135 versions:\u003c\/strong\u003e SVBONY also makes 57°–40° and 60°–40° versions with wider fields.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/w9105b-3_20250807161536_7516.jpg?v=1791670292\" alt=\"SVBONY SV135 7-21mm zoom eyepiece 1.25 inch barrel with safety undercut\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eField narrows to 36° at 21 mm:\u003c\/strong\u003e narrower than a fixed eyepiece of that focal length.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEye relief:\u003c\/strong\u003e 13–14 mm, workable with many glasses but shorter than the 57°–40° SV135.\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. It inserts into a 1.25″ focuser or diagonal; twist the barrel to zoom and touch up focus.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat magnification will I get?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eYour telescope's focal length divided by 7 and by 21 — about 143× to 48× on a 1000 mm telescope.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow is it different from the other SV135 zooms?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eThis is the lightest (95 g) with a 3-group, 5-element design and a 52°–36° field; the 57°–40° and 60°–40° versions use more elements for wider fields.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eIn short: a 95 g, fully multi-coated 1.25″ 7–21 mm zoom with a 52°–36° field — one eyepiece covering lunar and planetary magnifications.\u003c\/p\u003e","brand":"SvBony","offers":[{"title":"Default Title","offer_id":67722265067631,"sku":"W9105B","price":38.75,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/w9105b-0_20251230160657_4003.webp?v=1791670292","url":"https:\/\/ontariotelescope.com\/products\/svbony-sv135-7-21mm-zoom-eyepiece-52-36","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}