{"product_id":"svbony-sv221-1-25-45-degree-erect-prism-diagonal","title":"SVBONY SV221 1.25″ 45° Erect-Image Prism Diagonal","description":"\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6382466889884136253897484.jpg?v=1791669977\" alt=\"SVBONY SV221 1.25 inch 45 degree correct image prism diagonal 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 SV221 is a 1.25″ prism diagonal that turns the light path through 45° and delivers an erect, non-reversed image – right-side-up and correct left-to-right. It has a 19 mm clear aperture, a multi-coated prism and an optical length of about 86 mm. The housing combines ABS with aluminium end barrels, the nosepiece carries an M28.5 x 0.6 filter thread, the eyepiece holder clamps by screw with a brass compression ring, and the diagonal weighs 79 g (2.78 oz).\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThis is a good match if you use a refractor or a Maksutov or Schmidt-Cassegrain for both daytime terrestrial viewing and night-sky observing and want an image that matches what you see with your eyes, at a comfortable 45° viewing angle.\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6385726473051115629530435.jpg?v=1791669978\" alt=\"SVBONY SV221 45 degree diagonal 1.25 inch barrel and eyepiece holder\" 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\u003eErect, non-reversed image:\u003c\/strong\u003e correct orientation for terrestrial targets and easier star-hopping with a printed chart.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e45° deflection:\u003c\/strong\u003e a natural angle for viewing objects low on the horizon and land targets.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMulti-coated prism:\u003c\/strong\u003e SVBONY specifies higher light transmission.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilter thread:\u003c\/strong\u003e M28.5 x 0.6 inside the nosepiece for 1.25″ filters, with internal blackening.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBrass compression ring:\u003c\/strong\u003e brass locking screws and ring protect eyepiece and barrel finishes.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6385726475849621144304119.jpg?v=1791669977\" alt=\"SVBONY SV221 45 degree diagonal aluminium barrels and coated prism\" 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\/6385726477847577129682512.jpg?v=1791669977\" alt=\"SVBONY SV221 45 degree diagonal 1.25 inch filter thread\" 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\/6385726479343277608978085.jpg?v=1791669977\" alt=\"SVBONY SV221 45 degree diagonal brass compression ring\" 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\u003eLunar and planetary observing\u003c\/strong\u003e, which SVBONY lists as its main night-sky use.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTerrestrial viewing and birding\u003c\/strong\u003e through a small refractor.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePublic outreach and casual sessions\u003c\/strong\u003e, where an upright image is easier for everyone at the eyepiece.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6385726481941620816678671.jpg?v=1791669978\" alt=\"SVBONY SV221 45 degree diagonal for Moon and planet viewing\" 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\u003eTelescopes:\u003c\/strong\u003e refractors and catadioptrics such as Schmidt-Cassegrain and Maksutov-Cassegrain telescopes with a 1.25″ visual back.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEyepieces:\u003c\/strong\u003e any 1.25″ eyepiece.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilters:\u003c\/strong\u003e M28.5 x 0.6 thread on the nosepiece.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNewtonians and Dobsonians:\u003c\/strong\u003e these do not use a diagonal, and SVBONY does not recommend the SV221 for them.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eWhat's in the Box\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e1 x SV221 1.25″ 45° correct-image prism diagonal\u003c\/li\u003e\n\u003cli\u003e3 x M3 screws\u003c\/li\u003e\n\u003cli\u003e1 x dust cap\u003c\/li\u003e\n\u003cli\u003e1 x dust plug\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6385726483057733706721669.jpg?v=1791669977\" alt=\"SVBONY SV221 45 degree diagonal package contents\" 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\u003e1.25″ only:\u003c\/strong\u003e the barrel and eyepiece holder take 1.25″ accessories.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOptical length about 86 mm:\u003c\/strong\u003e if your telescope has limited inward focus travel, send us the model and we will confirm it reaches focus with this diagonal.\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 slides into the telescope's 1.25″ focuser or visual back and the eyepiece locks into it with the thumbscrew.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat does erect image mean?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eThe view is right-side-up and not mirror-reversed, the same orientation you see with your eyes.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I use it at night?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eYes. SVBONY lists it for Moon and planet viewing, alongside daytime targets.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill it work on my Newtonian?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eNewtonian and Dobsonian telescopes do not use a diagonal, so it is not intended for them.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eIn short: a 79 g, 1.25″ 45° prism diagonal with an erect, non-reversed image and filter threads for refractors and catadioptric telescopes used both day and night.\u003c\/p\u003e","brand":"SvBony","offers":[{"title":"Default Title","offer_id":67722333716591,"sku":"W9178B","price":25.07,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/w9178b_20250806143657_4091_20260810135616_0538.webp?v=1791670572","url":"https:\/\/ontariotelescope.com\/products\/svbony-sv221-1-25-45-degree-erect-prism-diagonal","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}