{"product_id":"svbony-sv135-7-21mm-zoom-eyepiece-57-40","title":"SVBONY SV135 1.25″ 7–21mm 57°–40° Zoom Eyepiece","description":"\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6387038656382229122243062.jpg\" alt=\"SVBONY SV135 7-21mm 57-40 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 is a 1.25″ zoom eyepiece that covers 7 mm to 21 mm with a twist of the barrel, giving a 57° apparent field at the short end and 40° at the long end. It uses a fully multi-coated 4-group, 6-element design, keeps 16.3–18 mm of eye relief across the range, and has an M28.5 × 0.6 thread for 1.25″ filters. It is 93 mm long and weighs 133 g.\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6387089713054019584231556.jpg\" alt=\"SVBONY SV135 zoom eyepiece focal length range\" style=\"max-width:100%;height:auto;\"\u003e\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 eyepiece that covers the most-used magnification range in a 1.25″ focuser — framing a target at 21 mm, then zooming in to 7 mm when the seeing allows — for the Moon, planets, double stars and star clusters. The 16.3–18 mm eye relief suits observers who keep their glasses on.\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 without swapping eyepieces.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e57°–40° apparent field:\u003c\/strong\u003e widest at 7 mm, where a wider field helps keep planets in view on an undriven mount.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e16.3–18 mm eye relief:\u003c\/strong\u003e comfortable with or without eyeglasses.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFully multi-coated optics:\u003c\/strong\u003e 4 groups, 6 elements.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAluminium housing with rubberized collar:\u003c\/strong\u003e non-slip grip, including in the cold or with gloves.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eM28.5 × 0.6 filter thread:\u003c\/strong\u003e takes SVBONY and other standard 1.25″ filters.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6387030927267458094266616.jpg\" alt=\"SVBONY SV135 zoom eyepiece multi-coated optics\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6387056370938381184609973.jpg\" alt=\"SVBONY SV135 zoom eyepiece smooth zoom mechanism\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6387039780022816254828456.jpg\" alt=\"SVBONY SV135 zoom eyepiece aluminium housing and grip\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eOptical Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe SV135 is a linear zoom: the focal length changes in proportion to the barrel rotation, with six elements in four groups and full multi-coating on the air-glass surfaces. As in most zooms, the apparent field narrows as focal length increases — here from 57° at 7 mm to 40° at 21 mm — while eye relief stays between 16.3 mm and 18 mm. On a 1000 mm focal-length telescope, the range works out to roughly 48× to 143×.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary observing:\u003c\/strong\u003e zoom in to match the seeing on Jupiter, Saturn and Mars.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLunar observing:\u003c\/strong\u003e move from whole-disc views to crater detail.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStar clusters and double stars:\u003c\/strong\u003e frame at 21 mm, then tighten.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOutreach and travel kits:\u003c\/strong\u003e one eyepiece in place of three or four.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6387037775927770828101338.jpg\" alt=\"SVBONY SV135 zoom eyepiece filter thread\" 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\u003eBarrel:\u003c\/strong\u003e 1.25″, fits standard 1.25″ focusers and diagonals.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilters:\u003c\/strong\u003e M28.5 × 0.6 thread for SVBONY 1.25″ filters.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBundles:\u003c\/strong\u003e SVBONY also offers this eyepiece in bundles with the SV188P and other accessories; contact us if you would like one of those combinations.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6380488605269154815957243.jpg\" alt=\"SVBONY SV135 zoom eyepiece eye relief for eyeglass wearers\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6380488603942389369532969.jpg\" alt=\"SVBONY SV135 zoom eyepiece 1.25 inch barrel\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6380488608242116548192749.jpg\" alt=\"SVBONY SV135 zoom eyepiece dimensions\" 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 with focal length:\u003c\/strong\u003e 40° at 21 mm is narrower than a fixed wide-field eyepiece of the same focal length.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25″ only:\u003c\/strong\u003e there is no 2″ barrel.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThree SV135 versions:\u003c\/strong\u003e SVBONY sells 52°–36°, 57°–40° (this one) and 60°–40° versions with different optical designs and weights.\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 drops into a 1.25″ focuser or diagonal like any eyepiece; twist the barrel to zoom and refocus as needed.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I use it for astrophotography?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eIt is a visual eyepiece. It can be used for simple eyepiece-projection or smartphone shots, but its main purpose is observing.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat magnification will I get?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eDivide your telescope's focal length by 7 and by 21. On a 1000 mm telescope that is about 143× at 7 mm and 48× at 21 mm.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow does it differ from the other SV135 versions?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eThis version has a 4-group, 6-element design with a 57°–40° field and 16.3–18 mm eye relief; the 52°–36° version uses 3 groups\/5 elements and the 60°–40° version 4 groups\/7 elements.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eIn short: a 133 g, 1.25″ zoom eyepiece covering 7–21 mm with a 57°–40° field and 16.3–18 mm eye relief — a single eyepiece for lunar, planetary and cluster observing.\u003c\/p\u003e","brand":"SvBony","offers":[{"title":"SV135","offer_id":67722219225199,"sku":"W9105A","price":59.85,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/w9105a-0_20251231152339_2821.webp?v=1791670075","url":"https:\/\/ontariotelescope.com\/products\/svbony-sv135-7-21mm-zoom-eyepiece-57-40","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}