{"product_id":"svbony-sv221-45-correct-image-prism-diagonal-125in","title":"SVBONY SV221 45° Correct Image Prism Diagonal - 1.25\"","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eProduces a fully erect, non-reversed image\u003c\/li\u003e\n\u003cli\u003eComfortable 45° viewing angle for terrestrial observation\u003c\/li\u003e\n\u003cli\u003eStandard 1.25\" barrel fits most refractor telescopes\u003c\/li\u003e\n\u003cli\u003eFeatures a 19mm clear aperture\u003c\/li\u003e\n\u003cli\u003eThreaded (M28.5x0.6) to accept 1.25\" filters\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eSVBONY SV221 45-Degree Erecting Prism Diagonal for Refractor Telescope\u003c\/h2\u003e\n\u003cp\u003eThe SVBONY SV221 converts your refractor for terrestrial viewing, delivering a fully erect, non-reversed image at a comfortable 45° angle. It fits standard 1.25 inch focusers, features a 19mm clear aperture for bright views, and adds approximately 86mm of optical length to your light path. Weighing only 79g, this multi-coated prism diagonal is threaded for M28.5x0.6 filters, making it a lightweight and versatile addition to your kit.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eCorrect-Image Views at a Comfortable 45° Angle\u003c\/h3\u003e\n\u003cp\u003eThe primary function of the SV221 is to correct the inverted and reversed image produced by a refractor telescope. Its internal prism system delivers an erect, non-reversed view, just as you see with your naked eye, making it intuitive to track moving subjects like birds, ships, or wildlife. The 45° deflection provides a much more comfortable viewing posture for daytime observation compared to looking straight through the telescope.\u003c\/p\u003e\n\u003cp\u003eThe multi-coated prism and 19mm clear aperture ensure that the image remains bright and clear. This makes the SV221 an essential accessory for transforming your astronomical refractor into a powerful, long-range spotting scope for terrestrial use.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eSecure Clamping and 1.25\" Filter Compatibility\u003c\/h3\u003e\n\u003cp\u003eThe SV221 is constructed with a durable, precision-molded plastic main body and machined aluminum barrels for a secure fit. Unlike basic diagonals that use a single screw to hold the eyepiece, this model features a brass compression ring that provides a firm, even grip without scratching or marring your eyepiece barrels. This secure connection maintains optical alignment and protects your equipment.\u003c\/p\u003e\n\u003cp\u003eFor added versatility, the 1.25\" nosepiece is threaded for standard M28.5x0.6 filters. You can easily attach a moon filter, a light pollution filter, or colored planetary filters to enhance your views without needing a separate filter cell.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eSV221 Erecting Prism vs. a Standard Mirror Diagonal\u003c\/h3\u003e\n\u003cp\u003eIt's important to choose the right diagonal for your purpose. While both redirect light for comfortable viewing, they produce very different images.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eStandard Mirror Diagonal:\u003c\/strong\u003e A typical \"star diagonal\" uses a mirror to bend the light path. This produces an image that is upright but reversed left-to-right. This is perfectly acceptable for astronomy, as stars are points of light, but it can be disorienting for terrestrial viewing where \"left is left\" matters.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSVBONY SV221 Erecting Prism:\u003c\/strong\u003e This diagonal uses a prism to provide a fully corrected image—upright and not reversed. This is the ideal choice for daytime, terrestrial observation with a refractor or Maksutov-Cassegrain, as it makes panning and tracking objects natural and intuitive.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy do I need the SVBONY SV221 for daytime viewing with my refractor?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA refractor telescope naturally produces an image that is upside-down and backward. The SVBONY SV221 uses a 45° prism to correct this, delivering an \u003cstrong\u003eerect and non-reversed image\u003c\/strong\u003e. This makes it possible to use your astronomy telescope as a high-power spotting scope for activities like birdwatching or landscape viewing.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the SVBONY SV221 work with my Newtonian telescope?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo. The SVBONY SV221 is designed for refractor and Cassegrain-type telescopes. A Newtonian reflector does not have enough focuser travel to reach focus with the additional \u003cstrong\u003e86mm optical length\u003c\/strong\u003e of a prism diagonal. Newtonians require very low-profile focusers and do not typically use diagonals in the same way.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use 1.25\" filters with the SVBONY SV221 diagonal?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The 1.25\" barrel of the SV221 has standard \u003cstrong\u003eM28.5x0.6 filter threads\u003c\/strong\u003e. This allows you to attach any standard 1.25\" filter, such as a moon filter for reducing glare or a light pollution filter for enhancing contrast on celestial objects.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the advantage of the SVBONY SV221's clamping system?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe SV221 features a brass compression ring inside the eyepiece holder. When you tighten the screw, this ring tightens evenly around the eyepiece barrel. This is superior to a simple screw which can scratch or dent your eyepieces and potentially cause a slight tilt.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the SVBONY SV221 suitable for high-magnification planetary viewing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile the SVBONY SV221 can be used for astronomy, it is primarily optimized for lower-power terrestrial viewing. Prism diagonals can sometimes introduce a small amount of chromatic aberration (false color) at very high magnifications. For critical, high-power observation of planets like Jupiter or Saturn, a high-quality mirror diagonal is often preferred by discerning astronomers.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the 45° angle of the SV221 affect observing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003e45° angle\u003c\/strong\u003e is ideal for terrestrial viewing, as you are typically looking at objects at or near the horizon. This provides a comfortable, natural neck position. For astronomical viewing, a 90° diagonal is often preferred, as it makes it easier to view objects that are high overhead, near the zenith.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eSVBONY\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eModel\u003c\/td\u003e\n\u003ctd\u003eSV221\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Design\u003c\/td\u003e\n\u003ctd\u003ePrism Diagonal\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBarrel Size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDeflection Angle\u003c\/td\u003e\n\u003ctd\u003e45°\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eImage Orientation\u003c\/td\u003e\n\u003ctd\u003eErect image, non-reversed\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eClear Aperture\u003c\/td\u003e\n\u003ctd\u003e19mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoatings\u003c\/td\u003e\n\u003ctd\u003eMulti-Coated (MC)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eEyepiece Connection\u003c\/td\u003e\n\u003ctd\u003e1.25\" Clamp with Screw\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Threads\u003c\/td\u003e\n\u003ctd\u003eM28.5x0.6\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Length\u003c\/td\u003e\n\u003ctd\u003eappr. 86mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaterial\u003c\/td\u003e\n\u003ctd\u003ePlastic \u0026amp; Metal\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet Weight\u003c\/td\u003e\n\u003ctd\u003e79g \/ 2.78oz\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eSV221 1.25\" 45 Degree Correct Image Prism Diagonal\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eM3 Screws\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 3\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eDust Cap\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eDust Plug\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/svbony-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eSVBONY Warranty Policy\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"SVBONY","offers":[{"title":"Default Title","offer_id":52861237592349,"sku":"SV-W9178B","price":17.59,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/SVBONY-SV221-45-Degree-Erecting-Prism-Diagonal-for-Refractor-Telescope-1_1489e9fd-f5d1-483a-8a02-fee8a0ff304d.jpg?v=1788883589","url":"https:\/\/davidastro.com\/en-us\/products\/svbony-sv221-45-correct-image-prism-diagonal-125in","provider":"David Astro","version":"1.0","type":"link"}