{"product_id":"baader-planetarium-m48-extension-tube-7-5-mm","title":"Baader Planetarium M48 Extension Tube – 7.5 mm","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eAdds 7.5 mm of optical path length\u003c\/li\u003e\n\u003cli\u003eStandard M48 x 0.75 female and male threads\u003c\/li\u003e\n\u003cli\u003ePrecision-machined for a rigid, tilt-free connection\u003c\/li\u003e\n\u003cli\u003eMatte black interior to prevent internal reflections\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\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\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\u003eM48 Extension Tube – 7.5 mm\u003c\/h2\u003e\n      \u003cp\u003eThe Baader M48 Extension Tube adds exactly 7.5 mm of length to your imaging train, providing a critical tool for achieving precise back focus with M48-threaded accessories. This component is essential for fine-tuning the distance between field flatteners, coma correctors, and your camera sensor.\u003c\/p\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\n  \u003cdiv class=\"DAV-bg-light\"\u003e\n    \u003cdiv class=\"DAV-section\"\u003e\n      \u003ch3\u003eFine-Tune Your Imaging Train with 7.5 mm of Extension\u003c\/h3\u003e\n      \u003cp\u003eOptical correctors like field flatteners and reducers demand exact spacing to deliver sharp stars across the entire frame. This 7.5 mm extension tube provides a crucial intermediate step when standard 5 mm or 10 mm extensions are too short or too long. It allows you to dial in the perfect distance with sub-millimeter accuracy by combining it with other spacers.\u003c\/p\u003e\n      \u003cul\u003e\n        \u003cli\u003e\n\u003cstrong\u003eEliminate Star Elongation:\u003c\/strong\u003e Achieve the exact back focus required by your optics to correct for coma and field curvature, turning elongated edge-of-field stars into sharp points.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003eBridge Small Gaps:\u003c\/strong\u003e Use this 7.5 mm tube to fill small, calculated gaps in your optical train, especially when accommodating off-axis guiders or filter wheels.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003eStackable Design:\u003c\/strong\u003e Combine with other M48 extensions and tuning rings to build up any custom spacing distance your imaging setup requires.\u003c\/li\u003e\n      \u003c\/ul\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\n  \u003cdiv class=\"DAV-bg-light\"\u003e\n    \u003cdiv class=\"DAV-section\"\u003e\n      \u003ch3\u003eRigid M48 Connection for Modern Cameras\u003c\/h3\u003e\n      \u003cp\u003eThis extension tube features standard M48 x 0.75 threads for a secure, non-flexing fit between your components. Unlike older T-2 connections, the larger M48 format is better suited for full-frame sensors, minimizing the risk of vignetting. The tube is engineered to integrate with modern cameras and accessories that often have very specific and minimal spacing tolerances.\u003c\/p\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\n\n\u003c\/div\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the primary use for the Baader 7.5 mm M48 Extension Tube?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eIts primary use is for \u003cstrong\u003eback focus adjustment\u003c\/strong\u003e in an astrophotography imaging train. Optical correctors (like field flatteners or coma correctors) require a precise distance to the camera sensor to work correctly. This 7.5 mm tube helps you achieve that exact distance when other components don't add up perfectly.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I know if I need a 7.5 mm M48 tube for my setup?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eYou need to calculate the total back focus of your current imaging train. Start with the required back focus of your flattener\/reducer (e.g., 55 mm). Then, add up the optical path length of every component after it: your off-axis guider, filter wheel, and the camera's sensor flange distance. If the total is, for example, 47.5 mm, this 7.5 mm extension tube will provide the exact spacing needed to reach 55 mm.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eCan I stack this 7.5 mm M48 Extension Tube with other extensions?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eYes, absolutely. These tubes are designed to be stacked to create custom lengths. For maximum rigidity, it is always best to use a single extension of the correct length if possible. However, stacking a few high-quality tubes like this Baader extension is a common and effective practice for achieving precise spacing.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWill adding the M48 Extension Tube – 7.5 mm cause vignetting?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eBecause it uses the large \u003cstrong\u003eM48 (2-inch) thread standard\u003c\/strong\u003e, this extension tube is designed to prevent vignetting on sensors up to full-frame (35mm) format. Vignetting is more likely to be caused by other components in the optical train, such as a smaller T-2 (M42) threaded item, rather than this M48 extension.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow can the 7.5 mm M48 tube help with a Baader MPCC Mark III on a Newtonian?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe Baader MPCC Mark III coma corrector requires a nominal back focus of 55 mm. If you are using a DSLR with a standard 44 mm flange distance and a 10 mm T-ring, you are already at 54 mm. A 1 mm M48 tuning ring would be ideal. However, if you are using a dedicated astronomy camera with a shorter back focus, like a ZWO camera with a 17.5 mm flange distance, you will need to add spacers. This 7.5 mm tube can be part of the combination of extensions needed to build up the remaining 37.5 mm distance.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eI have a Celestron EdgeHD with a 0.7x reducer. How would this 7.5 mm M48 tube be useful?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe Celestron 0.7x reducer for EdgeHD scopes requires a very generous 146 mm of back focus. This distance must accommodate an off-axis guider, filter wheel, and camera. The 7.5 mm M48 tube is perfect for the final fine-tuning stage. After you've assembled your main components and larger extensions, you can use this smaller tube to precisely dial in the last few millimeters to hit that 146 mm target perfectly.\u003c\/p\u003e\n  \u003c\/div\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Length\u003c\/td\u003e\n\u003ctd\u003e7.5 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eInner\/Outer Thread\u003c\/td\u003e\n\u003ctd\u003eM48 (2\")\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight (kg)\u003c\/td\u003e\n\u003ctd\u003e0.01\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompatible Brands\u003c\/td\u003e\n\u003ctd\u003eBaader Planetarium\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eClamping System\u003c\/td\u003e\n\u003ctd\u003eno clamp\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eInner Diameter \/ Clear Aperture (mm)\u003c\/td\u003e\n\u003ctd\u003e45 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOuter Diameter\u003c\/td\u003e\n\u003ctd\u003e53 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType of Adapter\u003c\/td\u003e\n\u003ctd\u003eExtension\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\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\"\u003eM48 Extension Tube – 7.5 mm\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\u003cp\u003eNo product-specific downloads are available for this item.\u003c\/p\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/baader-planetarium-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eBaader Planetarium 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Baader Planetarium","offers":[{"title":"7.5 mm","offer_id":52913159110941,"sku":"BAA-2958607","price":36.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/BaaderPlanetarium-M48-Extension-Tube-7-5-mm-1_726b05fb-0d1a-494b-a993-a5899186beaa.jpg?v=1789086912","url":"https:\/\/davidastro.com\/en-us\/products\/baader-planetarium-m48-extension-tube-7-5-mm","provider":"David Astro","version":"1.0","type":"link"}