{"product_id":"orion-optics-uk-odk12tr-optical-tube-assembly","title":"Orion Optics UK ODK12Tr Truss Optical Tube Assembly","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e300mm (12\") Optimized Dall-Kirkham Astrograph\u003c\/li\u003e\n\u003cli\u003e2040mm Focal Length (f\/6.8)\u003c\/li\u003e\n\u003cli\u003e\u0026gt;52mm Flat, Corrected Image Circle\u003c\/li\u003e\n\u003cli\u003e1.8µm On-Axis Spot Size\u003c\/li\u003e\n\u003cli\u003eCarbon Fiber Truss Tube Construction\u003c\/li\u003e\n\u003cli\u003e218mm of Back Focus\u003c\/li\u003e\n\u003cli\u003e3\" Crayford Focuser with 10:1 Reduction\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 ODK12Tr Truss Optical Tube Assembly\u003c\/h2\u003e\n\u003cp\u003eThe Orion Optics UK ODK12Tr Truss is a dedicated imaging platform built around a 300mm primary mirror with a 2040mm focal length. Its f\/6.8 corrected Dall-Kirkham design delivers incredibly small 1.8µm spot sizes on-axis and maintains a flat field greater than 52mm in diameter. The entire carbon fiber truss assembly weighs approximately 19kg and provides a generous 218mm of back focal distance for complex accessory stacks.\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\u003e300mm f\/6.8 Optics: 5.6µm Spots Across a \u0026gt;52mm Field\u003c\/h3\u003e\n\u003cp\u003eThe ODK12Tr's optical system is engineered for large-format sensors. The 300mm primary mirror operates at f\/6.8, providing enough image scale for detailed views of distant galaxies without demanding excessively long exposure times. A built-in, multi-coated 3-lens corrector flattens the field, delivering pinpoint stars with a spot size of just 5.6µm at the edge of a massive 52mm image circle—fully illuminating full-frame and larger sensors.\u003c\/p\u003e\n\u003cp\u003eThe 120mm secondary mirror provides this wide-field illumination, creating a 40% central obstruction by diameter. This is a necessary trade-off for edge-to-edge performance on large chips and has minimal impact on deep-sky imaging, where light grasp and field flatness are paramount.\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\u003eCarbon Fiber Truss: A 19kg Platform for Stable Imaging\u003c\/h3\u003e\n\u003cp\u003eConstructed from a carbon fiber sandwich material, the ODK12Tr's open truss frame offers exceptional thermal and mechanical stability. Weighing approximately 19kg, the tube assembly is rigid enough to support heavy imaging loads without flexure. The carbon fiber's near-zero coefficient of thermal expansion means the 2040mm focal length remains constant as temperatures drop, preventing focus shift during long imaging sessions.\u003c\/p\u003e\n\u003cp\u003eThe open truss design allows the 300mm primary mirror to acclimate to ambient temperatures quickly, aided by three controllable fans integrated into the honeycomb CNC-machined mirror cell. This active thermal management ensures your images are sharp from the start of the night to the end.\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\u003e218mm Back Focus \u0026amp; 3\" Focuser: Ready for Any Imaging Train\u003c\/h3\u003e\n\u003cp\u003eThe ODK12Tr is designed to accommodate any modern imaging accessory. It provides 218mm of back focal distance measured from the rear of the mirror cell, offering ample room for off-axis guiders, filter wheels, rotators, and large-format cameras. You won't need to compromise on your ideal setup due to spacing constraints.\u003c\/p\u003e\n\u003cp\u003eTo carry this load, the OTA is equipped with a robust 3\" Crayford focuser featuring a 10:1 reduction for precise, repeatable fine adjustments. The large drawtube diameter prevents vignetting with large sensors and ensures your entire imaging train is held securely throughout the night.\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\u003eODK12Tr vs. Ritchey-Chrétien: Collimation and Field Correction\u003c\/h3\u003e\n\u003cp\u003eUnlike Ritchey-Chrétien (RC) telescopes that use two difficult-to-align hyperbolic mirrors, the Optimized Dall-Kirkham (ODK) design employs an elliptical primary and a spherical secondary. This makes collimation significantly more forgiving and stable, saving valuable clear-sky time.\u003c\/p\u003e\n\u003cp\u003eWhile a classic Dall-Kirkham suffers from off-axis coma, the ODK12Tr's integrated 3-lens corrector completely eliminates it, producing a wide, flat, coma-free field that rivals the best RCs. The result is an astrograph that combines the optical simplicity and collimation stability of the DK design with the professional, wide-field imaging results of a corrected RC.\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 sensor size can the ODK12Tr fully illuminate and correct?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe ODK12Tr provides a fully corrected, flat field size of \u003cstrong\u003eover 52mm in diameter\u003c\/strong\u003e. This is large enough to cover full-frame (36x24mm) and even larger format astronomy sensors without significant vignetting or distortion at the corners.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the ODK12Tr's carbon fiber truss help with astrophotography?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe carbon fiber construction offers two key benefits. First, it has an extremely low coefficient of thermal expansion, which means the telescope's \u003cstrong\u003e2040mm focal length does not change\u003c\/strong\u003e as temperatures drop overnight, preventing focus shift. Second, the open truss design allows the primary mirror to cool down to ambient temperature much faster, aided by the \u003cstrong\u003ethree integrated cooling fans\u003c\/strong\u003e.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would the ODK12Tr perform on a large target like the Andromeda Galaxy (M31)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe ODK12Tr is an excellent choice for M31. Its \u003cstrong\u003e2040mm focal length\u003c\/strong\u003e and \u003cstrong\u003e300mm aperture\u003c\/strong\u003e provide the necessary resolution to capture fine dust lanes and star-forming regions within the galaxy's spiral arms. The \u003cstrong\u003e\u0026gt;52mm corrected field\u003c\/strong\u003e allows you to frame a significant portion of the galaxy and its companions in a single shot with a large-format camera.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the benefit of the ODK12Tr's 218mm of back focus?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003e218mm of back focus\u003c\/strong\u003e is exceptionally generous and provides critical flexibility for building your imaging train. It ensures you have enough space to install multiple accessories—such as an off-axis guider, a filter wheel, an adaptive optics unit, and a rotator—between the focuser and the camera sensor without running out of focus travel.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the ODK12Tr's f\/6.8 focal ratio good for imaging smaller targets like the Ring Nebula (M57)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, the f\/6.8 focal ratio is a versatile sweet spot. For a target like M57, the \u003cstrong\u003e2040mm focal length\u003c\/strong\u003e yields a large enough image scale to clearly resolve the nebula's ring structure and the faint central star. The focal ratio is still fast enough to capture significant signal in reasonable sub-exposure times, making it efficient for both broadband and narrowband imaging.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy choose the ODK12Tr over a comparable Ritchey-Chrétien astrograph?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe primary advantage of the ODK12Tr is its ease of collimation. Ritchey-Chrétien designs use two hyperbolic mirrors that are notoriously difficult to align perfectly. The ODK's elliptical primary and spherical secondary are far more tolerant, holding collimation better and being easier to adjust. With its integrated corrector, the ODK provides the flat, coma-free field of an RC without the collimation challenges.\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\u003eOptical Design\u003c\/td\u003e\n\u003ctd\u003eOptimized Dall-Kirkham (Corrected)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePrimary Mirror Diameter\u003c\/td\u003e\n\u003ctd\u003e300mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal Length\u003c\/td\u003e\n\u003ctd\u003e2040mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal Ratio\u003c\/td\u003e\n\u003ctd\u003ef\/6.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCorrected Field Size\u003c\/td\u003e\n\u003ctd\u003e\u0026gt;52mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpot Size (On-Axis)\u003c\/td\u003e\n\u003ctd\u003e1.8µm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpot Size (Field Edge)\u003c\/td\u003e\n\u003ctd\u003e5.6µm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSecondary Mirror Size\u003c\/td\u003e\n\u003ctd\u003e120mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocuser\u003c\/td\u003e\n\u003ctd\u003e3\" Crayford with 10:1 reduction\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBack Focus\u003c\/td\u003e\n\u003ctd\u003e218mm (from rear of mirror cell)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTube Material\u003c\/td\u003e\n\u003ctd\u003eCarbon fibre sandwich\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTube Length\u003c\/td\u003e\n\u003ctd\u003e615mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTube Diameter\u003c\/td\u003e\n\u003ctd\u003e350mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTube Weight\u003c\/td\u003e\n\u003ctd\u003eapprox. 19kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMirror Cell\u003c\/td\u003e\n\u003ctd\u003eHoneycomb CNC machined aluminium\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCooling System\u003c\/td\u003e\n\u003ctd\u003e3 controllable fans\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAttachment\u003c\/td\u003e\n\u003ctd\u003eCNC machined aluminium dovetail plate\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\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":52942365786397,"sku":"OOUK-ODK12TR-OPTICAL-TUBE-ASSEMBLY","price":11432.65,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Orion-Optics-UK-Logo_4e6790da-dd7f-4ac3-a55a-cf0778c4f563.jpg?v=1789606931","url":"https:\/\/davidastro.com\/en-us\/products\/orion-optics-uk-odk12tr-optical-tube-assembly","provider":"David Astro","version":"1.0","type":"link"}