{"product_id":"svbony-sv157-56mm-extension-tube-125in","title":"SVBONY SV157 56mm Extension Tube - 1.25\"","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eAdds a fixed 56mm or 70mm of back focus\u003c\/li\u003e\n\u003cli\u003eStandard 1.25-inch barrel diameter\u003c\/li\u003e\n\u003cli\u003eCNC-machined aluminum for rigidity\u003c\/li\u003e\n\u003cli\u003eMatte black interior prevents internal reflections\u003c\/li\u003e\n\u003cli\u003eSolves focusing issues with cameras and certain eyepieces\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 SV157 1.25-inch Extension Tube (56mm \/ 70mm)\u003c\/h2\u003e\n\u003cp\u003eThe SVBONY SV157 1.25-inch Extension Tube solves common focusing problems by providing a fixed 56mm or 70mm of additional length to your optical path. Constructed from CNC-machined aluminum, it ensures a rigid, non-flexing connection for any standard 1.25-inch focuser, diagonal, or accessory, making it an essential tool for both imaging and visual astronomy.\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\u003eAchieve Critical Focus: Adding 56mm or 70mm of Optical Path\u003c\/h3\u003e\n\u003cp\u003eCertain cameras, particularly DSLRs, have sensors that are too recessed to reach focus in telescopes with limited focuser travel. The SV157 extension tube bridges this gap, pushing the focal plane outwards to meet your sensor. It is also essential for using eyepieces that require significant out-travel, especially in reflector telescopes or when using accessories like focal reducers.\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\u003eCNC-Machined Construction for a Secure 1.25-inch Fit\u003c\/h3\u003e\n\u003cp\u003eUnlike plastic alternatives, the SV157 is machined from a single piece of aluminum for maximum rigidity and durability. This prevents any sag or tilt, even when supporting a heavy eyepiece or camera, which is critical for maintaining sharp, round stars across the field. The interior is blackened to absorb stray light, protecting your images and views from contrast-robbing reflections.\u003c\/p\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\"\u003eWhen would I need the SV157 1.25-inch Extension Tube with my Newtonian reflector and a DSLR camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eMany Newtonian reflectors do not have enough \"out-travel\" on their focusers to bring a DSLR camera's sensor to the focal plane for prime-focus astrophotography. The \u003cstrong\u003eSVBONY SV157\u003c\/strong\u003e adds the necessary length to the optical path, allowing you to achieve a sharp, infinity focus that would otherwise be impossible.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI can't get my short-focal-length eyepiece to focus in my Maksutov-Cassegrain. Will the SV157 extension tube help?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, it's a common issue. Some eyepieces, especially those with Barlows or other optical groups, require more outward focuser travel than a Maksutov's internal focusing mechanism can provide. The \u003cstrong\u003eSV157 1.25-inch Extension Tube\u003c\/strong\u003e can provide the extra distance needed to bring these specific eyepieces into a sharp focus.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I choose between the 56mm and 70mm SV157 extension tube?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe choice depends entirely on how much extra focus travel you need. It's best to measure the gap by first trying to focus your equipment and estimating the remaining distance. Since these are fixed-length tubes, choosing the one closest to your required distance is ideal. The \u003cstrong\u003e56mm\u003c\/strong\u003e is a good general-purpose starting point, while the \u003cstrong\u003e70mm\u003c\/strong\u003e is for systems with a significant focus shortfall.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I stack multiple SV157 extension tubes?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, you can stack multiple tubes to achieve longer extensions. However, be mindful that creating a very long, unbraced accessory train can introduce flexure or place excessive leverage on your focuser. For very long extensions, a single, longer tube is often a more stable solution.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the SVBONY SV157 add any optical distortion to my view?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo. Because the SV157 is a hollow tube with no lenses or glass elements, it does not alter the optical properties of your telescope. It purely serves as a mechanical spacer to extend the focal plane, so it will not introduce chromatic aberration, astigmatism, or other distortions.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the inside of the SV157 tube blackened to prevent reflections?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, the interior of the \u003cstrong\u003eSVBONY SV157\u003c\/strong\u003e extension tube is painted matte black and machined with light-baffling ridges. This is a critical feature that prevents stray light from reflecting off the inner walls and reducing the contrast of your images or visual field.\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\u003eBarrel Size\u003c\/td\u003e\n\u003ctd\u003e1.25 inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Lengths\u003c\/td\u003e\n\u003ctd\u003e56mm \/ 70mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaterial\u003c\/td\u003e\n\u003ctd\u003eCNC-machined aluminum\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\"\u003eSV157 1.25-inch Extension Tube\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\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":52861243097373,"sku":"SV-W9118A","price":11.19,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/SVBONY-SV157-1-25inch-Extension-Tube-56mm-70mm-1_b3053bb1-d7c6-494a-9f78-fe3adbf74ce1.jpg?v=1788660511","url":"https:\/\/davidastro.com\/en-us\/products\/svbony-sv157-56mm-extension-tube-125in","provider":"David Astro","version":"1.0","type":"link"}