{"product_id":"svbony-sv221-1-25-90-degree-mirror-diagonal","title":"SVBONY SV221 1.25″ 90° Mirror Diagonal","description":"\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6385741516607160316958546.jpg?v=1791669981\" alt=\"SVBONY SV221 1.25 inch 90 degree mirror 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 90° is a 1.25″ mirror star diagonal that turns the light path through a right angle so you can look down into the eyepiece rather than crouching behind the telescope. The aluminium-coated mirror has a reflectivity above 92% and a clear aperture of 29.5 mm, the optical length is about 73 mm, and the diagonal weighs 90.5 g (3.19 oz). The nosepiece carries an M28.5 x 0.6 filter thread, and the eyepiece holder uses a brass pressure ring and screw clamp.\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 with a refractor, Maksutov-Cassegrain or Schmidt-Cassegrain and want a light, inexpensive 1.25″ diagonal for comfortable viewing near the zenith, or a spare diagonal for a travel or grab-and-go telescope.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e90° right-angle design:\u003c\/strong\u003e comfortable viewing posture, especially for objects high in the sky.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAluminium-coated mirror:\u003c\/strong\u003e reflectivity above 92%.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e29.5 mm clear aperture:\u003c\/strong\u003e full illumination for 1.25″ eyepieces.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBrass pressure ring:\u003c\/strong\u003e holds the eyepiece without the screw touching its barrel.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLight construction:\u003c\/strong\u003e ABS housing with aluminium barrels, brass lock screws and a dust cover; 90.5 g in total.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6385741519395048632772069.jpg?v=1791669981\" alt=\"SVBONY SV221 90 degree diagonal aluminium die structure\" 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\/6385741521399283119833394.jpg?v=1791669981\" alt=\"SVBONY SV221 90 degree diagonal brass pressure 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, planetary and deep-sky observing\u003c\/strong\u003e with 1.25″ eyepieces.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eComfortable viewing near the zenith\u003c\/strong\u003e on refractors and catadioptrics.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCasual daytime viewing and birding,\u003c\/strong\u003e keeping in mind the mirror-reversed image described below.\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\u003eTelescopes:\u003c\/strong\u003e refractors and catadioptrics such as Schmidt-Cassegrain and Maksutov-Cassegrain telescopes with a 1.25″ focuser or 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\u003eImage orientation:\u003c\/strong\u003e upright but mirror-reversed left to right, as with any single-mirror diagonal. The SV221 45° prism version gives a fully correct image if you need one for land viewing.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/6385741525434271981431665.jpg?v=1791669982\" alt=\"SVBONY SV221 mirror diagonal image orientation versus normal image\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eWhat's in the Box\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e1 x SV221 1.25″ 90° mirror 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\/6385741529117361807069902.jpg?v=1791669982\" alt=\"SVBONY SV221 90 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\u003eMirror-reversed image:\u003c\/strong\u003e normal for astronomy; for land viewing an erect-image prism diagonal gives a correct view.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNewtonians and Dobsonians:\u003c\/strong\u003e these telescopes do not use a diagonal, and SVBONY does not recommend the SV221 for them.\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 1.25″ focuser or visual back, and the eyepiece locks into it with the thumbscrew and brass ring.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes it reverse the image?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eThe image is upright but reversed left to right, which is standard for a mirror diagonal.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I add filters?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eYes. 1.25″ filters thread into the M28.5 x 0.6 nosepiece.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill it fit my telescope?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eIt fits any refractor or catadioptric with a 1.25″ focuser or visual back.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eIn short: a light 1.25″ 90° mirror diagonal with a 29.5 mm aperture, over 92% reflectivity, a brass compression ring and filter threads for refractors and catadioptric telescopes.\u003c\/p\u003e","brand":"SvBony","offers":[{"title":"Default Title","offer_id":67722340171887,"sku":"W9178A","price":21.36,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/w9178a_20250806150235_2192_20260810144007_6755.webp?v=1791670612","url":"https:\/\/ontariotelescope.com\/products\/svbony-sv221-1-25-90-degree-mirror-diagonal","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}