{"product_id":"orion-optics-uk-odk12-optical-tube-assembly","title":"Orion Optics UK ODK12 Optical Tube Assembly","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e300mm (12\") Optimised Dall-Kirkham Optics\u003c\/li\u003e\n\u003cli\u003e2040mm Focal Length at a fast f\/6.8 Focal Ratio\u003c\/li\u003e\n\u003cli\u003eCovers a greater than 52mm flat imaging circle\u003c\/li\u003e\n\u003cli\u003eDelivers 1.8µm on-axis spot sizes\u003c\/li\u003e\n\u003cli\u003eGenerous 218mm of back focal distance\u003c\/li\u003e\n\u003cli\u003eThermally stable carbon fibre sandwich tube construction\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 ODK12 Optical Tube Assembly\u003c\/h2\u003e\n\u003cp\u003eThe Orion Optics UK ODK12 is an astrograph engineered for large-format imaging, combining a 300mm primary mirror and a 2040mm focal length into a fast f\/6.8 system. Its integrated multi-coated 3-lens corrector produces a flat field greater than 52mm in diameter, delivering pinpoint stars with a spot size of just 1.8µm on-axis. The entire optical system is housed in a 625mm long carbon fibre sandwich tube that weighs approximately 19kg, ensuring thermal stability for critical imaging.\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\u003eODK Astrograph: 52mm Flat Field with 1.8µm Stars\u003c\/h3\u003e\n\u003cp\u003eThe Optimised Dall-Kirkham (ODK) design is built from the ground up for astrophotography. The ODK12 uses a 300mm primary mirror and a matched 120mm secondary, with a built-in 3-lens corrector group to eliminate off-axis coma and field curvature. This results in a corrected image circle larger than 52mm, capable of illuminating the largest commercially available astronomy camera sensors without vignetting or distortion.\u003c\/p\u003e\n\u003cp\u003eThe optical correction delivers incredibly tight stars across this massive field. On-axis spot sizes are a mere 1.8µm, and even at the extreme edge of the field, stars remain compact at 5.6µm. This level of correction ensures that you are capturing all the resolution the 300mm aperture can provide, making the ODK12 a premier instrument for high-resolution mosaics and large-field imaging of nebulae and galaxy clusters.\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 Tube \u0026amp; Active Cooling at 19kg\u003c\/h3\u003e\n\u003cp\u003eTo maintain focus stability during temperature drops, the ODK12 features a carbon fibre sandwich tube. This material has virtually zero thermal expansion, preventing the 2040mm focal plane from shifting during long exposures or throughout an imaging session. The tube's open design and short 625mm length promote rapid thermal acclimation.\u003c\/p\u003e\n\u003cp\u003eThis process is accelerated by three controllable cooling fans mounted behind the honeycomb CNC-machined primary mirror cell. This active cooling system quickly brings the 300mm mirror to ambient temperature, minimizing tube currents and ensuring the sharpest possible images from the moment you begin observing. At approximately 19kg, the OTA is manageable for observatory-class mounts rated for higher payloads.\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 with a 3\" Crayford Focuser\u003c\/h3\u003e\n\u003cp\u003eA critical feature for serious imagers is ample back focus, and the ODK12 provides an exceptionally long 218mm of working distance from the rear of the mirror cell. This generous space allows you to assemble a complete imaging train with any combination of accessories—including off-axis guiders, large filter wheels, rotators, and adaptive optics—without concern for reaching focus.\u003c\/p\u003e\n\u003cp\u003eFocusing is controlled by a robust 3\" Crayford focuser with a 10:1 dual-speed reduction mechanism for precise adjustments. This heavy-duty focuser is designed to carry the weight of modern large-format cameras and accessory stacks without flexure or slippage, ensuring your focal plane remains locked and perfectly orthogonal to the optical axis.\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\u003eODK12 vs. 12\" Ritchey-Chrétien: Collimation and Correction\u003c\/h3\u003e\n\u003cp\u003eThe ODK12 is often compared to Ritchey-Chrétien (RC) astrographs of similar aperture. While RCs are renowned for their corrected fields, they have a key disadvantage.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eRC Advantage:\u003c\/strong\u003e Ritchey-Chrétien telescopes typically feature longer focal ratios (f\/8 or slower), which can provide more image scale for smaller targets without the need for Barlow lenses.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eODK12 Advantage:\u003c\/strong\u003e The ODK is significantly easier to collimate. Unlike an RC, which requires precise alignment of both the primary and secondary mirrors, the ODK's primary mirror is fixed. Collimation is achieved by adjusting the secondary mirror only, a much simpler and more stable process. Furthermore, the ODK's 3-lens corrector is an integrated part of the design, whereas many RCs require an additional, separate corrector to achieve a fully flat field.\u003c\/li\u003e\n\u003c\/ul\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 class of mount is required for the ODK12 OTA?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWith a tube weight of approximately \u003cstrong\u003e19kg (42 lbs)\u003c\/strong\u003e, the ODK12 requires a robust, observatory-grade equatorial mount. For imaging, you should select a mount with a payload capacity of at least 60-70 lbs to comfortably handle the OTA plus the additional weight of your camera, guider, and accessories.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhich cameras are best suited for the ODK12's 52mm image circle?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe ODK12's greater than \u003cstrong\u003e52mm flat field\u003c\/strong\u003e is designed for cameras with large, full-frame (36x24mm) or larger sensors. Cameras like the ZWO ASI6200, QHY600, or models with the KAF-16803 sensor will be fully illuminated, allowing you to capture vast fields of view, such as the entire Andromeda Galaxy (M31) and its companions in a single frame.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the ODK12's f\/6.8 focal ratio benefit deep-sky imaging?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003ef\/6.8\u003c\/strong\u003e focal ratio is a sweet spot for deep-sky imaging. It is fast enough to collect significant signal on faint nebulae and galaxies in shorter sub-exposures compared to slower f\/8 or f\/10 systems. At the same time, its \u003cstrong\u003e2040mm focal length\u003c\/strong\u003e provides enough image scale to resolve fine details in targets like the Whirlpool Galaxy (M51) or planetary nebulae.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does the ODK12's 218mm back focal distance allow me to do?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003e218mm back focal distance\u003c\/strong\u003e provides enormous flexibility for building your imaging train. It ensures you can fit a full stack of accessories, such as an off-axis guider, a large 3\" filter wheel, a camera rotator, and your camera, and still easily reach focus. This is a critical feature that many other astrographs lack.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs collimating the ODK12 difficult?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, the ODK12 is designed for straightforward collimation. Unlike Ritchey-Chrétien designs that require careful alignment of both mirrors, the ODK's primary mirror is fixed. You only need to adjust the secondary mirror, which is a much simpler and more stable procedure, making it easier to maintain perfect optical alignment.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill I experience focus shift with the ODK12's carbon fiber tube?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003ecarbon fibre sandwich\u003c\/strong\u003e tube material is specifically chosen for its near-zero coefficient of thermal expansion. This means that as the ambient temperature changes during an imaging session, the \u003cstrong\u003e625mm\u003c\/strong\u003e tube will not shrink or expand, keeping the focal plane stable and eliminating the need for constant refocusing.\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\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\u003eBack Focal Distance\u003c\/td\u003e\n\u003ctd\u003e218mm (from rear of mirror cell)\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\u003eCorrector Design\u003c\/td\u003e\n\u003ctd\u003eMulti-coated 3 lens\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\u003e625mm\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 with supports\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":52942365131037,"sku":"OOUK-ODK12-OPTICAL-TUBE-ASSEMBLY","price":13321.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/OrionOpticsUK-ODK12-Optical-Tube-Assembly-1_99c581f4-5562-4d1c-8b5f-39440e50ce50.jpg?v=1789606897","url":"https:\/\/davidastro.com\/products\/orion-optics-uk-odk12-optical-tube-assembly","provider":"David Astro","version":"1.0","type":"link"}