{"product_id":"svbony-sv109-m42-variable-extension-tube","title":"SVBONY SV109 M42 Variable Extension Tube","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eVariable Extension Range: 24mm to 35mm\u003c\/li\u003e\n\u003cli\u003eMale Thread: M42*0.75 (T2-thread)\u003c\/li\u003e\n\u003cli\u003eFemale Thread: M42*0.75 (T2-thread)\u003c\/li\u003e\n\u003cli\u003eAll-Metal Construction\u003c\/li\u003e\n\u003cli\u003eBlack Anodized Finish\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 SV109 Variable M42 Thread Extension Tube\u003c\/h2\u003e\n\u003cp\u003eThe SVBONY SV109 Variable M42 Thread Extension Tube provides a critical range of adjustment from 24mm to 35mm, allowing you to precisely set the back focus of your imaging train. With standard M42*0.75 threads on both male and female ends, it integrates seamlessly into any T2-threaded setup to achieve optimal spacing for field flatteners, reducers, and off-axis guiders.\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\u003eFine-Tune Your Imaging Train: 24mm to 35mm of Variable Spacing\u003c\/h3\u003e\n\u003cp\u003eAchieving the exact back focus specified by your corrector is non-negotiable for sharp, flat-field images. The SV109 extension tube replaces a whole set of fixed spacers, offering a continuous adjustment range from 24mm to 35mm. This allows you to dial in the perfect distance with sub-millimeter precision, compensating for filter thickness and sensor depth variations without needing to stack multiple rings.\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 M42*0.75 Threading for Any Accessory\u003c\/h3\u003e\n\u003cp\u003eBuilt with all-metal construction and a durable black anodized finish, the SV109 ensures a rigid, non-reflective connection in your optical path. The universal M42*0.75 T2-threads provide compatibility with the vast majority of astronomy cameras, filter wheels, off-axis guiders, and other accessories, eliminating any concerns about flexure or unstable connections.\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\u003eSV109 vs. Fixed Spacers: Why Variable Extension Matters\u003c\/h3\u003e\n\u003cp\u003eWhile fixed T2 spacer rings can get you close to the correct back focus, they rarely get you there exactly. The SV109's variable 24-35mm length gives you the ability to make minute adjustments on the fly. This is invaluable when you add or change a filter, which alters the optical path length, or when trying to perfectly position a guide camera prism relative to the main sensor.\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\"\u003eWhat is the primary use for the SVBONY SV109 extension tube?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe SVBONY SV109 is used to add a precise and adjustable amount of distance in an M42\/T2-threaded optical train. Its primary purpose is to achieve the critical \u003cstrong\u003eback focus distance\u003c\/strong\u003e required by field flatteners, coma correctors, and focal reducers for optimal astrophotography results.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I set a specific distance, like 30mm, with the SV109?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe SV109 adjusts by twisting the two barrels. To set a specific distance, you can use a digital caliper to measure the extension as you adjust it. Once the desired length is achieved, the friction of the mechanism holds the position securely.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the SV109 to achieve the standard 55mm back focus for my DSLR and coma corrector?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, the SV109 is a key component for achieving 55mm. A typical DSLR with a T-ring has about 55mm of back focus on its own. If you add a filter wheel or off-axis guider (which might use 20-30mm), the SV109's \u003cstrong\u003e24-35mm range\u003c\/strong\u003e is perfect for making up the remaining distance precisely.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the M42 threads on the SV109 connect to my Celestron T-adapter or ZWO camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The SV109 uses the astronomical standard M42*0.75 thread, commonly known as the T2-thread. This is the same thread used on virtually all Celestron T-adapters, ZWO and QHY astronomy cameras, and most filter wheels and off-axis guiders.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the SVBONY SV109 strong enough for a heavy astronomy camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe SVBONY SV109 features all-metal construction. It is designed to be rigid and can securely hold common cooled astronomy cameras and DSLRs without flexure, ensuring your imaging train remains perfectly aligned.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is the inside of the SV109 extension tube black?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe black anodized finish on both the interior and exterior surfaces minimizes stray light reflections. This is critical for maintaining high contrast in your images by preventing internal reflections from reaching the camera sensor.\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\u003eType\u003c\/td\u003e\n\u003ctd\u003eAstronomical T2 thread Extension Tube\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMale Thread\u003c\/td\u003e\n\u003ctd\u003eM42*0.75\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFemale Thread\u003c\/td\u003e\n\u003ctd\u003eM42*0.75\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVariable Extension\u003c\/td\u003e\n\u003ctd\u003e24-35mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eColor\u003c\/td\u003e\n\u003ctd\u003eBlack\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\"\u003eSV109 Variable M42 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 1-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"SVBONY","offers":[{"title":"Default Title","offer_id":52861259546909,"sku":"SV-F9180A","price":19.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/SVBONY-SV109-Variable-M42-Thread-Extension-Tube-1_0b834a10-c441-4ae7-a9e2-cad3ca34972e.jpg?v=1788660653","url":"https:\/\/davidastro.com\/fr-us\/products\/svbony-sv109-m42-variable-extension-tube","provider":"David Astro","version":"1.0","type":"link"}