{"product_id":"william-optics-d-dig2d-c-db-sct","title":"William Optics 2\" 90° Dura Bright Dielectric Diagonal for SCT threaded Scope","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eEnables use of 2-inch eyepieces for wide-field views\u003c\/li\u003e\n\u003cli\u003e90° viewing angle for comfortable observing at the zenith\u003c\/li\u003e\n\u003cli\u003eDura-Bright dielectric coatings for superior light transmission and durability\u003c\/li\u003e\n\u003cli\u003eThreads directly to the rear cell of SCT-threaded telescopes\u003c\/li\u003e\n\u003cli\u003eReduces mechanical flexure compared to standard slip-fit diagonals\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\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\u003e2\" 90° Dura Bright Dielectric Diagonal for SCT threaded Scope\u003c\/h2\u003e\n      \u003cp\u003eThis 2\" 90° Dura Bright Dielectric Diagonal is an essential upgrade for any Schmidt-Cassegrain telescope owner looking to maximize both optical throughput and mechanical stability. By threading directly onto your SCT's rear cell, it creates a solid, flex-free connection ideal for heavy 2-inch eyepieces and imaging equipment. The highly reflective and durable dielectric coatings ensure that the maximum amount of light from your telescope's optics reaches your eye, delivering brighter images and improved contrast on faint deep-sky objects.\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\u003eThe Stability of a Direct SCT Thread-On Connection\u003c\/h3\u003e\n      \u003cp\u003eUnlike standard diagonals that require a visual back and use a slip-fit compression ring, this model threads directly onto the rear port of most Schmidt-Cassegrain telescopes. This single, solid connection eliminates a common source of mechanical sag and potential misalignment, which is critical when using heavy, wide-field 2-inch eyepieces or a camera. Your optical train remains perfectly collinear, preserving the sharp focus your SCT is designed to deliver.\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\u003eDura-Bright Dielectric Coatings for Maximum Reflectivity\u003c\/h3\u003e\n      \u003cp\u003eThe \"Dura-Bright\" mirror features advanced dielectric coatings, which offer two key advantages over standard aluminum or silver coatings. First, they provide extremely high reflectivity across the visual spectrum, transmitting more light to the eyepiece for visibly brighter images. Second, these multi-layer coatings are far more durable and resistant to environmental degradation, ensuring your diagonal maintains its peak optical clarity for years of use without tarnishing.\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\u003eUnlocking Wide-Field Views with the 2-Inch Format\u003c\/h3\u003e\n      \u003cp\u003eThe primary reason to upgrade to a 2-inch diagonal is to gain access to the widest possible true fields of view your telescope can produce. By accommodating 2-inch eyepieces, this diagonal transforms your SCT into a capable instrument for sweeping the Milky Way and framing large celestial objects like the Andromeda Galaxy (M31) or the North American Nebula (NGC 7000) in a single view.\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\u003eSCT Thread-On vs. Slip-Fit Diagonals: Why Rigidity Matters\u003c\/h3\u003e\n      \u003cp\u003eFor an SCT owner, the choice between a thread-on and a slip-fit diagonal comes down to stability. While a slip-fit diagonal offers rotational convenience, it can also introduce tilt or sag, especially under the load of a heavy eyepiece like a Tele Vue Nagler or Ethos.\u003c\/p\u003e\n      \u003cul\u003e\n        \u003cli\u003e\n\u003cstrong\u003eThread-On Advantage:\u003c\/strong\u003e By becoming a rigid extension of the optical tube, a thread-on diagonal like this Dura Bright model maintains perfect alignment. This prevents focus shift and ensures that stars at the edge of the field remain as sharp as your telescope's optics will allow.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003eSlip-Fit Limitation:\u003c\/strong\u003e The small amount of play in a slip-fit connection can be enough to slightly degrade image sharpness, an issue that becomes more apparent during high-magnification planetary viewing or astrophotography.\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\"\u003eWhy should I upgrade to this 2\" Dura Bright SCT Diagonal from my stock 1.25\" diagonal?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eUpgrading to this 2\" diagonal offers three major improvements. You gain access to \u003cstrong\u003ewide-field 2-inch eyepieces\u003c\/strong\u003e, your views will be noticeably \u003cstrong\u003ebrighter due to the dielectric coatings\u003c\/strong\u003e, and the \u003cstrong\u003edirect SCT thread connection provides a more rigid and stable\u003c\/strong\u003e optical path than the standard visual back and slip-fit diagonal combination.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the main advantage of a \"dielectric\" diagonal?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eA dielectric diagonal uses dozens of micro-thin layers of optical coatings to achieve extremely high reflectivity. This means more light is sent to your eyepiece, making faint objects easier to see. These coatings are also incredibly durable and resistant to aging, so the mirror will not tarnish or lose reflectivity over time like a standard aluminum mirror can.\u003c\/p\u003e\n  \u003c\/div\u003e\n    \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWill this 2\" Dura Bright diagonal help me see faint objects like the Veil Nebula (NGC 6960) with my 8\" SCT?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eYes. The combination of using a 2-inch, low-power eyepiece and the high-reflectivity dielectric coatings is ideal for observing large, faint objects like the Veil Nebula. The wider field of view helps you frame the nebula, and the increased light transmission makes it appear brighter against the background sky, especially when paired with a UHC or O-III filter.\u003c\/p\u003e\n  \u003c\/div\u003e\n    \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow does this Dura Bright diagonal improve views of open clusters like the Pleiades (M45) in my Celestron 11\" SCT?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eA large SCT like an 11\" has a long focal length, making it difficult to fit large open clusters like the Pleiades into a single field of view with 1.25\" eyepieces. This 2\" diagonal allows you to use long focal length 2\" eyepieces, reducing the magnification and expanding your true field of view to frame the entire cluster beautifully.\u003c\/p\u003e\n  \u003c\/div\u003e\n    \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eDoes the direct-thread connection of this SCT diagonal prevent my eyepiece from rotating?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eYes, the diagonal body itself is fixed in place once threaded onto the telescope. However, the eyepiece holder on the diagonal typically uses a non-marring compression ring that allows you to rotate the eyepiece to the most comfortable viewing orientation without loosening the diagonal itself.\u003c\/p\u003e\n  \u003c\/div\u003e\n    \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use this Dura Bright SCT Diagonal on my refractor or Newtonian telescope?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eNo, not directly. This diagonal is designed specifically with SCT threads to attach to the rear cell of a Schmidt-Cassegrain or Maksutov-Cassegrain telescope. It does not have a 2\" nosepiece for use in a standard refractor or Newtonian focuser.\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\u003eSpecifications\u003c\/td\u003e\n\u003ctd\u003eNo specifications available for this product.\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\"\u003eBox Contents\u003c\/p\u003e\n        \u003cp class=\"DAV-item-subtitle\"\u003eBox contents have not been specified by the manufacturer.\u003c\/p\u003e\n      \u003c\/div\u003e\n    \u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/li\u003e\n\n\n\u003cli\u003e\n\u003cp\u003eWarranty information is not available for this product.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":52853691613469,"sku":"WO-D-DIG2D-C-DB-SCT","price":207.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/WilliamOptics-2-90-Dura-Bright-Dielectric-Diagonal-for-SCT-threaded-Scope-1_8816c6a4-d15b-4d84-afc9-ba6a23f3ec08.jpg?v=1788457875","url":"https:\/\/davidastro.com\/en-int\/products\/william-optics-d-dig2d-c-db-sct","provider":"David Astro","version":"1.0","type":"link"}