{"product_id":"orion-optics-uk-85mm-fixed-adaptor-ring-30mm-bfd","title":"Orion Optics UK 85mm Fixed Adaptor Ring with 30mm BFD","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eProvides a fixed 30mm back focus distance\u003c\/li\u003e\n\u003cli\u003eDesigned for 85mm threaded interfaces\u003c\/li\u003e\n\u003cli\u003eSolid, single-piece construction for maximum rigidity\u003c\/li\u003e\n\u003cli\u003eMachined in the UK by Orion Optics\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\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\u003eOrion Optics UK 85mm Fixed Adaptor Ring with 30mm BFD\u003c\/h2\u003e\n      \u003cp\u003eThe Orion Optics UK 85mm fixed adaptor ring is a precision-machined spacer that provides exactly 30mm of back focus distance (BFD), essential for building a rigid and accurate imaging train for astrophotography.\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\u003eAchieving a Fixed 30mm Back Focus with an 85mm Interface\u003c\/h3\u003e\n      \u003cp\u003eIn astrophotography, achieving the precise back focus specified by a field flattener or reducer is critical for sharp stars across the entire frame. This 85mm fixed adaptor ring is engineered to provide exactly 30mm of spacing, eliminating the guesswork and potential flexure of adjustable systems.\u003c\/p\u003e\n      \u003cp\u003eThe single-piece design ensures a perfectly rigid connection between your components, preventing tilt that can ruin an otherwise perfect image. While it lacks the flexibility of variable spacers, its strength and precision make it the ideal choice when your required spacing is exactly 30mm.\u003c\/p\u003e\n      \u003cul\u003e\n        \u003cli\u003e\n\u003cstrong\u003eZero Flexure:\u003c\/strong\u003e The solid, fixed-length construction is inherently more stable than multi-part adjustable spacers, ensuring your camera sensor remains perfectly parallel to the focal plane.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003ePrecise Spacing:\u003c\/strong\u003e Delivers a non-negotiable 30mm of distance, crucial for optical correctors that have strict back focus tolerances for optimal performance.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003eLarge Aperture:\u003c\/strong\u003e The 85mm diameter provides a wide, unvignetted light path suitable for large format sensors when used with a compatible optical system.\u003c\/li\u003e\n      \u003c\/ul\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\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 purpose of the Orion Optics UK 85mm fixed adaptor ring?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThis component is a precision spacer. It's designed to establish an exact \u003cstrong\u003e30mm distance\u003c\/strong\u003e between two parts of an optical train that use an \u003cstrong\u003e85mm thread\u003c\/strong\u003e, such as between a focuser and a camera setup. This is critical for achieving the correct back focus distance required by field flatteners or coma correctors.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does \"30mm BFD\" mean for my astrophotography setup?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eBFD stands for \u003cstrong\u003eBack Focus Distance\u003c\/strong\u003e. Most optical correctors require the imaging sensor to be placed at a very specific distance to deliver sharp, aberration-free stars. This 30mm adaptor ring is used as a component to help achieve that exact total distance.\u003c\/p\u003e\n  \u003c\/div\u003e\n    \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eIs this 85mm adaptor compatible with my specific telescope or camera?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eCompatibility is determined by the physical threads on your equipment. This adaptor is designed for an \u003cstrong\u003e85mm diameter threaded interface\u003c\/strong\u003e. You must confirm that the components you intend to connect both have matching 85mm threads before purchasing.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhy should I choose a fixed 30mm adaptor instead of an adjustable spacer?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eA fixed adaptor like this Orion Optics UK ring offers superior \u003cstrong\u003erigidity and stability\u003c\/strong\u003e. It eliminates the potential for tilt or flexure that can be introduced by adjustable, multi-part spacers, ensuring a solid and square connection. The trade-off is its lack of adjustability; it is only useful when you need exactly 30mm of spacing.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I calculate if the Orion Optics UK 30mm ring is the right spacer for my imaging train?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eFirst, identify the total back focus requirement of your flattener or reducer (e.g., 55mm is common). Next, add up the back focus contributed by your camera, filter wheel, and any other accessories. If the remaining distance needed is exactly 30mm, this adaptor is the correct component for your setup.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWill this Orion Optics UK 85mm adaptor cause vignetting with my full-frame sensor?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe large \u003cstrong\u003e85mm clear aperture\u003c\/strong\u003e of this ring is generally sufficient to prevent it from being the source of vignetting, even with full-frame sensors. However, vignetting is a property of the entire optical system, so final performance also depends on your telescope's focuser, corrector, and any other adaptors in the light path.\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\u003eInterface Diameter\u003c\/td\u003e\n\u003ctd\u003e85mm\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eBack Focus Provided\u003c\/td\u003e\n\u003ctd\u003e30mm\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eType\u003c\/td\u003e\n\u003ctd\u003eFixed Adaptor Ring \/ Spacer\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eManufacturer\u003c\/td\u003e\n\u003ctd\u003eOrion Optics UK\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\"\u003e85mm fixed adaptor ring (30mm BFD)\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\/orion-optics-uk-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eOrion Optics UK 1-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Orion Optics UK","offers":[{"title":"Default Title","offer_id":52942444462365,"sku":"OOUK-85MM-FIXED-ADAPTOR-RING-30MM","price":141.11,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Orion-Optics-UK-Logo_de5a0fcc-efa5-4e9f-9631-1705d8c28210.jpg?v=1789607609","url":"https:\/\/davidastro.com\/en-us\/products\/orion-optics-uk-85mm-fixed-adaptor-ring-30mm-bfd","provider":"David Astro","version":"1.0","type":"link"}