{"product_id":"orion-optics-uk-85mm-fixed-adaptor-ring-25mm-bfd","title":"Orion Optics UK 85mm Fixed Adaptor Ring - 25mm BFD","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eConnects to 85mm threaded correctors and accessories\u003c\/li\u003e\n\u003cli\u003eProvides a fixed 25mm of back focus distance (BFD)\u003c\/li\u003e\n\u003cli\u003eEngineered for Orion Optics UK imaging systems\u003c\/li\u003e\n\u003cli\u003eSolid, single-piece construction prevents flexure and tilt\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\u003eOrion Optics UK 85mm Fixed Adaptor Ring - 25mm BFD\u003c\/h2\u003e\n\u003cp\u003eThe Orion Optics UK 85mm fixed adaptor ring provides a precise 25mm of back focus distance (BFD), an essential component for achieving a perfectly flat field with specific Orion Optics UK correctors and imaging systems. This adapter ensures your camera sensor is placed at the exact focal plane required for sharp, pinpoint stars across the entire frame.\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\u003eThe Orion Optics UK 25mm BFD Adapter for 85mm Correctors\u003c\/h3\u003e\n\u003cp\u003eThis adapter is designed to integrate seamlessly into imaging trains that utilize an 85mm thread, common on larger field flatteners and coma correctors from Orion Optics UK. Achieving the specified 25mm back focus is not optional; it is a critical requirement for the optical system to perform as designed, eliminating field curvature and other aberrations.\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\u003eWhy a Fixed 25mm Spacer Beats Adjustable Rings\u003c\/h3\u003e\n\u003cp\u003eWhile adjustable spacers offer flexibility, this fixed 25mm adapter provides absolute rigidity. Its single-piece metal construction eliminates the possibility of tilt or flexure that can occur in adjustable, multi-part extension tubes, especially under the load of a heavy astronomy camera. For serious astrophotography, this mechanical stability is key to consistent, high-quality data.\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 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 ring is a precision spacer. Its sole function is to connect to an \u003cstrong\u003e85mm threaded component\u003c\/strong\u003e in your optical train and provide exactly \u003cstrong\u003e25mm of back focus distance\u003c\/strong\u003e. This ensures your camera's sensor is positioned at the precise distance required by your telescope's field flattener or coma corrector for optimal performance.\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 exactly 25mm of back focus for my Orion Optics UK telescope?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe required back focus distance is determined by the specific corrector or flattener you are using, not the telescope itself. You should consult the technical documentation for your Orion Optics UK corrector to confirm if it requires a 25mm spacing for your imaging setup.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use this 85mm adapter with other brands of telescopes or correctors?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile it may be physically compatible with any system that uses an 85mm thread, this adapter is specifically machined to provide the 25mm back focus required by certain Orion Optics UK components. Using it with other systems may not place your sensor at the correct distance, potentially degrading image quality.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is this Orion Optics UK adapter a fixed 25mm length instead of being adjustable?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA fixed-length adapter offers superior mechanical stability. Unlike adjustable spacers, which can introduce sag or tilt from their multiple threaded parts, a single-piece fixed adapter ensures a rigid, perfectly aligned connection. This is critical for preventing misshapen stars, especially with heavier cameras.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill this 85mm adapter introduce any tilt into my imaging train?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo. This adapter is precision-machined as a single, solid component to prevent tilt. Its primary advantage over adjustable or stacked solutions is the guarantee of a square, rigid connection between your corrector and the next element in your imaging train.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat imaging setup would require a 25mm spacer like this one?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAn example setup would be connecting an Orion Optics UK coma corrector with an 85mm output thread to an off-axis guider or filter wheel that leaves a remaining 25mm distance requirement to reach the camera sensor's focal plane. This adapter fills that specific gap precisely.\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\u003eAdapter Type\u003c\/td\u003e\n\u003ctd\u003eFixed Adaptor Ring \/ Spacer\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eConnection 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\u003e25mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\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\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 (25mm 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\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":52942437941533,"sku":"OOUK-85MM-FIXED-ADAPTOR-RING-25MM","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_bcbcb78a-51d1-4c59-b783-e00d99d291c7.jpg?v=1789607593","url":"https:\/\/davidastro.com\/en-us\/products\/orion-optics-uk-85mm-fixed-adaptor-ring-25mm-bfd","provider":"David Astro","version":"1.0","type":"link"}