{"title":"William Optics Field Flatteners, Reducers \u0026 Coma Correctors","description":"\u003cp\u003eWilliam Optics field flatteners and reducers correct field curvature so stars stay round to the edge of the sensor, and the reducers also shorten the focal length for faster exposures. Several are adjustable, so the spacing can be tuned for different telescopes.\u003c\/p\u003e\u003cp\u003eThe range includes the Flat61 and Flat61R for the Z61, the Flat73A and Flat73R for the Z73, the Flat6AIII, the Flattener 68III, the 0.8x Reducer Flattener 7A, the 0.72x Reducer Flattener 8 and the Ultra Flat 132 and 156 0.79x reducers.\u003c\/p\u003e","products":[{"product_id":"william-optics-adjustable-flat61-for-z61","title":"William Optics Adjustable Flat61 for Z61","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e1.0x Flattener Power\u003c\/li\u003e\n\u003cli\u003eDesigned for William Optics Zenithstar 61\u003c\/li\u003e\n\u003cli\u003eFull-Frame Sensor Coverage\u003c\/li\u003e\n\u003cli\u003eAdjustable Back Focus Mechanism\u003c\/li\u003e\n\u003cli\u003eM54 Telescope Thread \u0026amp; M48 Camera Thread\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\u003eWilliam Optics Adjustable Flat61 for Z61\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Adjustable Flat61 is the definitive imaging accessory for the Zenithstar 61, delivering edge-to-edge pinpoint stars on sensors up to full-frame format at a native 1.0x power. Its 2-element, 2-group optical design corrects the field curvature inherent in a fast refractor, connecting to the telescope via a rigid M54 x 0.75 thread and to your camera with a standard M48 x 0.75 T-mount. Weighing just 272.8 g, the unit's optical path consists of the 39.5 mm flattener body and a 19 mm rotator and adapter section, engineered for precise spacing and image composition.\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\u003e1.0x Power for Full-Frame Correction with the Zenithstar 61\u003c\/h3\u003e\n\u003cp\u003eThis flattener corrects field curvature without altering the native focal length or focal ratio of your Z61 telescope. The 1.0x magnification ensures the field of view you framed visually is the same one you capture, preserving the telescope's original optical characteristics. The 2-element in 2-group lens design is optimized specifically for the Z61's optics, providing a flat, corrected image circle large enough to accommodate full-frame (36x24mm) sensors without vignetting or distorted stars at the corners.\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\u003eM54 Telescope Connection \u0026amp; M48 Camera Interface\u003c\/h3\u003e\n\u003cp\u003eThe Flat61A attaches to the Z61 focuser using a robust M54 x 0.75 threaded connection, eliminating any potential for tilt or flex that can occur with simple compression fittings. The camera side features the astrophotography standard M48 x 0.75 thread, providing a wide, secure aperture for filters and direct connection to dedicated astronomy cameras and a broad range of DSLR\/mirrorless T-mounts. The integrated rotator allows you to frame your target perfectly without loosening any threaded connections, maintaining rigid alignment throughout your imaging session.\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\u003eAdjustable Back Focus for Edge-to-Edge Sharpness\u003c\/h3\u003e\n\u003cp\u003eAchieving a perfectly flat field requires precise spacing between the flattener's rear element and the camera sensor. While fixed-length flatteners work well with a specific camera setup, the Adjustable Flat61 acknowledges that filter wheels, off-axis guiders, or different T-ring thicknesses can alter this critical distance. This unit's key feature is its ability to be fine-tuned, allowing you to dial in the exact back focus required by your unique imaging train to guarantee sharp stars across the entire frame, not just in the center.\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 William Optics Adjustable Flat61?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Flat61A is an optical corrector designed specifically for the William Optics Zenithstar 61 refractor. It flattens the curved focal plane of the telescope, ensuring that stars are sharp and pinpoint across the entire field of view, from the center to the corners of your camera sensor.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I connect the Flat61A to my Z61 and camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe flattener connects directly to the Z61 focuser's drawtube via a secure \u003cstrong\u003eM54 x 0.75 thread\u003c\/strong\u003e. The camera side features a standard \u003cstrong\u003eM48 x 0.75 thread\u003c\/strong\u003e, which is compatible with most dedicated astronomy cameras, filter wheels, and T-mounts for DSLR and mirrorless cameras.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is an adjustable flattener like the Flat61A better than a fixed one?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAn adjustable flattener provides the flexibility to achieve perfect back focus with various imaging setups. Different cameras, filter thicknesses, and adapters can slightly change the ideal spacing. The Flat61A allows you to fine-tune this distance, ensuring optimal optical correction regardless of the specific components in your imaging train.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDoes the Flat61A change the focal length of my Zenithstar 61?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo. The William Optics Flat61A is a \u003cstrong\u003e1.0x flattener\u003c\/strong\u003e, meaning it does not reduce or extend the telescope's focal length. It corrects for optical aberrations while preserving the Z61's native field of view and f-ratio.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the William Optics Flat61A with a full-frame camera like the Sony A7 series on my Z61?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The Flat61A is explicitly designed to provide a corrected image circle for \u003cstrong\u003eFull Frame\u003c\/strong\u003e sensors. With the appropriate M48 T-mount for Sony E-mount cameras (listed in the supported T-mounts), you can achieve a flat field with your Sony A7 series camera.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the Flat61A provide a flat field for imaging the Andromeda Galaxy (M31) with my Z61 and an APS-C camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAbsolutely. The flattener is designed for sensors up to full-frame, so it will provide excellent correction for smaller \u003cstrong\u003eAPS-C\u003c\/strong\u003e and \u003cstrong\u003eM4\/3\u003c\/strong\u003e sensors. It will ensure that all the stars across the vast expanse of the Andromeda Galaxy (M31) are rendered as sharp points.\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\u003eFlattener Power\u003c\/td\u003e\n\u003ctd\u003e1.0x\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Design\u003c\/td\u003e\n\u003ctd\u003e2 Elements in 2 Groups\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Format Support\u003c\/td\u003e\n\u003ctd\u003eFull Frame, APS-C, M4\/3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTelescope Connection\u003c\/td\u003e\n\u003ctd\u003eM54 x 0.75 x 5 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Connection\u003c\/td\u003e\n\u003ctd\u003eM48 x 0.75 x 4 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Path Components\u003c\/td\u003e\n\u003ctd\u003eFlattener 39.5 mm + Rotator\/Adapter 19 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSupported T-Mounts\u003c\/td\u003e\n\u003ctd\u003eCanon EF, RF; Nikon F, Z; Sony E; Pentax K; MFT (M4\/3); FUJI X\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e272.8 g (0.60 lbs)\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\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/william-optics-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eWilliam Optics 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":44967219822877,"sku":"WO-P-FLAT61A","price":384.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/William-Optics-Adjustable-Flat61-for-Z61-P-FLAT61A-1__32465.1596133236.1280.1280.jpg?v=1684339110"},{"product_id":"william-optics-adjustable-reducer-flattener-flat61r-for-z61","title":"William Optics Adjustable Reducer Flattener Flat61R for Z61","description":"\u003cul\u003e\n\t\u003cli\u003eAdjustable reducer and field flattener for William Optics Z61 telescope\u003c\/li\u003e\n\t\u003cli\u003eImproves image sharpness and reduces distortion\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\t\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cul class=\"tabs-content\"\u003e\n\t\u003cli class=\"active\"\u003e\n\t\t\u003cp\u003e\nThe William Optics Adjustable Reducer Flattener Flat61R is an essential accessory for the William Optics Z61 telescope. This adjustable reducer and field flattener enhances image sharpness and reduces distortion, ensuring high-quality astrophotography results.\n\t\t\u003c\/p\u003e\n\t\t\u003cdiv class=\"warning\"\u003e\n\t\t\t\u003cimg alt=\"Disclaimer\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/warning-logo.svg?v=1714663206\" width=\"25px\"\u003e\n\t\t\t\u003cp\u003e\nSpecifically designed for the William Optics Z61 telescope.\n\t\t\t\u003c\/p\u003e\n\t\t\u003c\/div\u003e\n\t\t\n\t\t\u003cdiv\u003e\n\t\t\t\u003ch3\u003eCompatibility\u003c\/h3\u003e\n\t\t\t\u003chr\u003e\n\t\t\t\u003cdiv class=\"two-columns-section\"\u003e\n\t\t\t\t\u003cdiv class=\"text-side-2\"\u003e\n\t\t\t\t\t\u003cp\u003e\nThe Flat61R is designed to perfectly fit the William Optics Z61 telescope. It ensures a seamless connection, enhancing the optical performance of your telescope.\n\t\t\t\t\t\u003c\/p\u003e\n\t\t\t\t\u003c\/div\u003e\n\t\t\t\t\u003cdiv class=\"image-side-2\" data-mce-style=\"text-align: start;\" style=\"text-align: start;\"\u003e\n\t\t\t\t\t\u003cimg alt=\"William Optics Adjustable Reducer Flattener Flat61R for Z61\" src=\"https:\/\/davidastro.com\/cdn\/shop\/files\/William-Optics-Adjustable-Reducer-Flattener-Flat61R-for-Z61-P-FLAT61R-2__19145.1596133238.1280.1280_832x832.jpg?v=1684339301\" style=\"margin-bottom: 16px; float: none;\"\u003e\n\t\t\t\t\u003c\/div\u003e\n\t\t\t\u003c\/div\u003e\n\n\t\t\t\u003cdiv data-mce-style=\"backgroundcolor: #0a0001; border-radius: 5px;\" style=\"background-color: #0a0001; border-radius: 5px;\"\u003e\n\t\t\t\t\u003ch3 style=\"color: white!important;\"\u003eEnhanced Image Quality\u003c\/h3\u003e\n\t\t\t\t\u003chr\u003e\n\t\t\t\t\u003cdiv class=\"two-columns-section\"\u003e\n\t\t\t\t\t\u003cdiv class=\"image-side-2\" data-mce-style=\"text-align: start;\" style=\"text-align: start;\"\u003e\n\t\t\t\t\t\t\u003cimg alt=\"William Optics Adjustable Reducer Flattener Flat61R for Z61\" src=\"https:\/\/davidastro.com\/cdn\/shop\/files\/William-Optics-Adjustable-Reducer-Flattener-Flat61R-for-Z61-P-FLAT61R-8__83135.1596133238.1280.1280_832x832.jpg?v=1684339311\" style=\"margin-bottom: 16px; float: none;\"\u003e\n\t\t\t\t\t\u003c\/div\u003e\n\t\t\t\t\t\u003cdiv class=\"text-side-2\"\u003e\n\t\t\t\t\t\t\u003cp style=\"color: white!important;\"\u003e\nThe adjustable reducer flattener improves image sharpness across the field, reducing optical aberrations and ensuring crisp, clear images of celestial objects.\n\t\t\t\t\t\t\u003c\/p\u003e\n\t\t\t\t\t\u003c\/div\u003e\n\t\t\t\t\u003c\/div\u003e\n\t\t\t\u003c\/div\u003e\n\t\t\u003c\/div\u003e\n\n\t\t\u003ch3\u003eAdjustable Design\u003c\/h3\u003e\n\t\t\u003chr\u003e\n\t\t\u003cp\u003e\nThe Flat61R features an adjustable design, allowing users to fine-tune the distance to the camera sensor for optimal performance, ensuring perfect star shapes across the entire image.\n\t\t\u003c\/p\u003e\n\t\t\n\t\t\u003ch3\u003eDurable Construction\u003c\/h3\u003e\n\t\t\u003chr\u003e\n\t\t\u003cp\u003e\nMade from high-quality materials, such as anodized aluminum, the Flat61R is built to last, providing durability and stability for all your astrophotography needs.\n\t\t\u003c\/p\u003e\n\n\t\t\u003ch3\u003ePrecision Engineering\u003c\/h3\u003e\n\t\t\u003chr\u003e\n\t\t\u003cp\u003e\nThe Flat61R is engineered with precision to ensure a tight and secure fit, minimizing any unwanted movement or vibrations and enhancing overall image quality.\n\t\t\u003c\/p\u003e\n\n\t\t\u003ch3\u003eEase of Use\u003c\/h3\u003e\n\t\t\u003chr\u003e\n\t\t\u003cp\u003e\nDesigned for easy attachment and detachment, the Flat61R allows users to quickly set up or dismantle their equipment as needed, making it convenient for field use.\n\t\t\u003c\/p\u003e\n\n\t\t\u003ch3\u003eVersatility\u003c\/h3\u003e\n\t\t\u003chr\u003e\n\t\t\u003cp\u003e\nIdeal for both astrophotography and observational astronomy, the Flat61R provides the necessary optical enhancements for detailed and high-quality imaging.\n\t\t\u003c\/p\u003e\n\t\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":44967220019485,"sku":"WO-P-FLAT61R","price":409.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/William-Optics-Adjustable-Reducer-Flattener-Flat61R-for-Z61-P-FLAT61R-1__95363.1596133238.1280.1280.jpg?v=1684339299"},{"product_id":"william-optics-flattener-68iii","title":"William Optics Flattener 68III","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e1.0x Flattener Power preserves native focal length\u003c\/li\u003e\n\u003cli\u003eCorrects field curvature for Full Frame sensors\u003c\/li\u003e\n\u003cli\u003eDesigned for William Optics FLT132, GT102, and GT153 refractors\u003c\/li\u003e\n\u003cli\u003eConnects via a robust M92 telescope-side thread\u003c\/li\u003e\n\u003cli\u003eFeatures a standard M48 camera-side thread to prevent vignetting\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\u003eWilliam Optics Flattener 68III\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Flattener 68III is an essential imaging accessory designed to deliver perfectly flat fields across full-frame sensors without altering your telescope's native focal length. This 1.0x flattener connects directly to the focuser of premier William Optics refractors like the FLT132, GT102, and GT153 via a secure M92 x 1 thread. Its efficient 2-element optical design corrects for field curvature, ensuring pinpoint stars from the center to the corners of your frame, while the M48 camera connection minimizes vignetting for modern DSLR and dedicated astronomy cameras.\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\u003e1.0x Flattening: Edge-to-Edge Correction for Full-Frame Sensors\u003c\/h3\u003e\n\u003cp\u003eThis flattener is engineered for the imaging purist. With a 1.0x power factor, it maintains your telescope's exact focal length and f-ratio, preserving the original image scale for maximum resolution on planetary and small deep-sky targets. The optical system, comprised of 2 elements in 2 groups, is fully multi-coated to ensure high light transmission and contrast, turning the curved focal plane of a fast refractor into a flat, corrected surface ready for large sensors.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFull Frame Illumination:\u003c\/strong\u003e Designed to fully illuminate and correct sensors up to a 44mm diagonal, making it ideal for full-frame (24x36mm), APS-C, and M4\/3 formats.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePinpoint Stars:\u003c\/strong\u003e Eliminates the elongated, comatic stars typically seen at the edges of uncorrected images, producing sharp, round stars across your entire field of view.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePreserves Native Scale:\u003c\/strong\u003e Unlike a reducer, this flattener allows you to image at your telescope's maximum magnification and resolution, ideal for detailed studies of galaxies and nebulae.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eM92 Interface: Optimized for William Optics FLT and GT Refractors\u003c\/h3\u003e\n\u003cp\u003eThe Flattener 68III creates a seamless, rigid connection with specific William Optics telescopes. It threads directly onto the M92 drawtube of the FLT132, GT102, and GT153 refractors, ensuring perfect alignment and eliminating any potential for flexure in the imaging train. This robust mechanical design is critical for supporting heavier camera packages.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eTelescope Connection:\u003c\/strong\u003e The M92 x 1 male thread provides a secure, direct-fit attachment to compatible William Optics focusers.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCamera Connection:\u003c\/strong\u003e A standard M48 x 0.75 female thread on the camera side offers a wider aperture than older T2 (M42) threads, preventing vignetting on full-frame sensors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBroad Camera Support:\u003c\/strong\u003e Compatible with standard M48 T-rings for Canon, Nikon, Sony, Pentax, MFT, and Fuji camera systems.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eA 64.5mm Optical Path with Precision Back-Focus Adjustment\u003c\/h3\u003e\n\u003cp\u003eAchieving perfect sensor-to-flattener spacing is critical for optimal correction, and the Flattener 68III is built with this in mind. The unit is adjustable, allowing you to precisely dial in the required back focus for your specific camera and filter setup. This fine-tuning capability ensures you can achieve the sharpest possible stars across the entire field, regardless of minor variations in your imaging train.\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 primary function of the William Optics Flattener 68III?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Flattener 68III is an optical corrector designed to eliminate field curvature in refractor telescopes. It ensures that stars are sharp and pinpoint not just in the center of the image, but all the way to the corners. As a \u003cstrong\u003e1.0x flattener\u003c\/strong\u003e, it accomplishes this without changing the telescope's native focal length or f-ratio.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhich telescopes is the Flattener 68III compatible with?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis flattener is specifically designed for a direct, threaded connection to the M92 focusers on the following William Optics models:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eFluorostar 132 (FLT132)\u003c\/li\u003e\n\u003cli\u003eGran Turismo 102 (GT102)\u003c\/li\u003e\n\u003cli\u003eGran Turismo 153 (GT153)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the Flattener 68III perform with a full-frame camera like a Sony A7 on the GT102?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eIt's an excellent match. The Flattener 68III is designed to correct the entire field of a full-frame sensor. When paired with a GT102, you can expect sharp, round stars across the entire 24x36mm sensor of a Sony A7-series camera, with minimal vignetting thanks to the M48 camera connection.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy should I choose this 1.0x Flattener 68III instead of a reducer\/flattener?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eChoose the 1.0x Flattener 68III when your primary goal is \u003cstrong\u003emaximum image resolution and scale\u003c\/strong\u003e. A reducer\/flattener makes your telescope \"faster\" and provides a wider field of view, but it shrinks the image. For detailed work on smaller galaxies or planetary nebulae where every bit of focal length matters, a 1.0x flattener is the superior choice.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does the \"adjustable\" feature of the Flattener 68III do?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe adjustable design allows you to make micro-adjustments to the back focus distance—the spacing between the flattener's rear lens and your camera sensor. This is crucial for achieving perfect corner-to-corner star sharpness, as it lets you compensate for the exact thickness of your adapters, filter wheels, or off-axis guiders.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the Flattener 68III work for imaging the full Andromeda Galaxy (M31) with an FLT132?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile the Flattener 68III will provide a perfectly corrected field, an FLT132 at its native focal length may be too magnified to capture the entire Andromeda Galaxy (M31) in a single frame, even with a full-frame sensor. For a target of that size with that telescope, a reducer\/flattener would be a better choice to achieve a wider field of view.\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\u003ePower\u003c\/td\u003e\n\u003ctd\u003e1.0 x\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Design\u003c\/td\u003e\n\u003ctd\u003e2 Elements in 2 Groups\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSupported Sensor Formats\u003c\/td\u003e\n\u003ctd\u003eFull Frame, APS-C, M4\/3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTelescope-Side Thread\u003c\/td\u003e\n\u003ctd\u003eM92 x 1 (Male)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera-Side Thread\u003c\/td\u003e\n\u003ctd\u003eM48 x 0.75 (Female)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Length\u003c\/td\u003e\n\u003ctd\u003e64.5 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Brand Support\u003c\/td\u003e\n\u003ctd\u003eCanon EF, RF, Nikon F, Z, Sony E, Pentax K, MFT (M4\/3), FUJI X\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e718.2 g \/ 1.58 lbs\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\"\u003eWilliam Optics Flattener 68III\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\/william-optics-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eWilliam Optics 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":44967220117789,"sku":"WO-P-FLAT68III","price":1087.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/William-Optics-Flattener-68III-P-FLAT68III-1__37693.1596133239.1280.1280.jpg?v=1684339133"},{"product_id":"william-optics-adjustable-flat6aiii","title":"William Optics Adjustable Flat6AIII","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e0.8x Focal Reducer \u0026amp; Field Flattener\u003c\/li\u003e\n\u003cli\u003eOptimized for GT71, GT81, Z81 \u0026amp; Z103 Refractors\u003c\/li\u003e\n\u003cli\u003eIlluminates Full-Frame Sensors\u003c\/li\u003e\n\u003cli\u003eAdjustable Back Focus Mechanism\u003c\/li\u003e\n\u003cli\u003eM63 Telescope-Side Thread\u003c\/li\u003e\n\u003cli\u003eM48 Camera-Side Thread with Filter Slot\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\u003eWilliam Optics Adjustable Flat6AIII 0.8x Reducer \u0026amp; Flattener\u003c\/h2\u003e\n      \u003cp\u003eThe William Optics Adjustable Flat6AIII is a 0.8x reducer and flattener engineered specifically to convert William Optics GT71, GT81, Z81, and Z103 refractors into flat-field astrographs. Its 3-element apochromatic optical design uses Ohara glass to correct for field curvature across 97% of a full-frame sensor, connecting directly to the telescope via an M63 thread and to your camera with a standard M48 T-mount.\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\u003e0.8x Reduction and 97% Full-Frame Illumination\u003c\/h3\u003e\n      \u003cp\u003eBy reducing your telescope's focal ratio by a factor of 0.8x, the Flat6AIII significantly shortens required exposure times and expands your field of view. This transforms a GT81 from f\/5.9 to a faster f\/4.7 system, allowing you to capture faint nebulosity in less time and frame larger targets like the Andromeda Galaxy (M31) or the North American Nebula (NGC 7000). The optical design provides excellent illumination and pinpoint stars across 97% of a full-frame sensor's diagonal.\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\u003eAPO Triplet Optics: A 3-Element Ohara Glass Design\u003c\/h3\u003e\n      \u003cp\u003eThe Flat6AIII employs a 3-element apochromatic (APO) lens design constructed from premium Ohara glass. This triplet configuration, combined with full multi-coatings, ensures high-contrast images free of distracting chromatic aberration. Where simpler flatteners can introduce bloated or discolored stars at the edge of the field, the Flat6AIII maintains sharp, color-pure stars right to the corners of your frame, preserving the optical integrity of your William Optics refractor.\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\u003eM63 Direct-Thread Integration for 4 William Optics Refractors\u003c\/h3\u003e\n      \u003cp\u003eThis flattener attaches directly to the focuser drawtube using a robust M63 thread, creating a solid, flex-free imaging train. This direct connection is superior to standard 2\" nosepiece adapters, which can introduce tilt. The body of the Flat6AIII is adjustable to set the precise back focus for your specific telescope, and an integrated M48 filter slot behind the camera threads allows for the easy installation of 2\" filters without adding extra accessories.\u003c\/p\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\"\u003eWhich William Optics telescopes is the Flat6AIII compatible with?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe William Optics Flat6AIII is specifically designed and optimized for four refractors: the \u003cstrong\u003eGT71\u003c\/strong\u003e, \u003cstrong\u003eGT81\u003c\/strong\u003e, \u003cstrong\u003eZ81\u003c\/strong\u003e, and \u003cstrong\u003eZ103\u003c\/strong\u003e. It connects via a direct M63 thread on these models.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the 0.8x reduction of the Flat6AIII benefit my imaging with a GT81?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe 0.8x reduction makes your telescope \"faster,\" meaning it gathers light more quickly. On a GT81 (f\/5.9), the Flat6AIII creates an f\/4.7 imaging system. This reduces your required exposure time by about 36%, allowing you to collect more data in a single night. It also provides a wider field of view to better frame large deep-sky objects.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use a full-frame DSLR like a Canon EOS Ra with the Flat6AIII?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eYes. The Flat6AIII is designed to fully illuminate and correct for full-frame sensors up to 44mm. You will need the appropriate M48 T-ring for your camera mount (e.g., Canon RF) to connect it to the flattener's M48 threads.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I attach the Flat6AIII to my telescope?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe Flat6AIII threads directly onto the focuser. You will first need to unthread and remove the standard 2\" eyepiece holder from your telescope's focuser. The flattener's M63 threads then screw directly onto the focuser drawtube for a secure, tilt-free connection.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use 2\" filters with the William Optics Flat6AIII?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eYes. The Flat6AIII has an integrated M48 x 0.75 filter thread just inside the camera-side connection. This allows you to thread in any standard 2\" astronomy filter (which uses M48 threads) for light pollution reduction or narrowband imaging.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does \"adjustable back focus\" mean on the Flat6AIII?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe body of the William Optics Flat6AIII can be extended or retracted to fine-tune the distance between the flattener's optics and your camera sensor. Each compatible telescope model requires a slightly different spacing for a perfectly flat field. This adjustability ensures you can achieve optimal optical correction without needing to add or remove spacers.\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\u003eFlattener Power\u003c\/td\u003e\n\u003ctd\u003e0.8 x\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eLens Design\u003c\/td\u003e\n\u003ctd\u003e3 Groups, 3 Elements\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eCamera Format Support\u003c\/td\u003e\n\u003ctd\u003eFull Frame, APS-C, M4\/3\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eTelescope Connection\u003c\/td\u003e\n\u003ctd\u003eM63 x 1 x 6 mm Thread\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eCamera Connection\u003c\/td\u003e\n\u003ctd\u003eM48 x 0.75 x 4 mm T-Mount Thread\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eCompatible T-Mounts\u003c\/td\u003e\n\u003ctd\u003eCanon EF, RF, Nikon F, Z, Sony E, Pentax K, MFT (M4\/3), FUJI X\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eOptical Length\u003c\/td\u003e\n\u003ctd\u003e61.5 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e519.4 g \/ 1.15 lbs\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  \u003c\/ul\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/william-optics-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eWilliam Optics 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":44967221002525,"sku":"WO-P-FLAT6AIII","price":371.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/William-Optics-FLAT6AIII__75538.1675887359.1280.1280.jpg?v=1684339316"},{"product_id":"william-optics-adjustable-flat73a-for-z73","title":"William Optics Adjustable Flat73A for Z73","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eDesigned specifically for the William Optics ZenithStar 73 APO\u003c\/li\u003e\n\u003cli\u003eDelivers a 1.0x, perfectly flat field across full-frame sensors\u003c\/li\u003e\n\u003cli\u003eConnects to the Z73 focuser via a secure M63 thread\u003c\/li\u003e\n\u003cli\u003eProvides a standard M48 x 0.75 thread for camera T-rings and accessories\u003c\/li\u003e\n\u003cli\u003eAdjustable design ensures precise back focus for a wide range of cameras\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\u003eDownloads\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\u003eWilliam Optics Adjustable Flat73A for Z73\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Adjustable Flat73A is the essential imaging accessory for the ZenithStar 73 telescope, engineered to eliminate field curvature across sensors up to full-frame size. This 1.0x flattener preserves the Z73's native focal length and f-ratio, connecting securely via its M63 thread and providing a standard M48 output for your camera. The 2-element optical design ensures that stars remain pinpoint sharp from the center of your image to the extreme corners.\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\u003eFull-Frame Correction at 1.0x Power\u003c\/h3\u003e\n\u003cp\u003eThe Flat73A uses a 2-element optical design in two groups to correct the field curvature inherent in the Z73's fast, wide-field optics. As a 1.0x flattener, it does not act as a reducer or extender, so your telescope's focal length and focal ratio remain unchanged. This design is optimized to illuminate and correct for sensors up to a full-frame format, making it ideal for DSLRs, mirrorless cameras, and large-chip dedicated astronomy cameras.\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\u003eZ73-Specific M63 Thread and M48 Camera Connection\u003c\/h3\u003e\n\u003cp\u003eDesigned for seamless integration, the Flat73A attaches directly to the ZenithStar 73's focuser drawtube using a robust M63 x 1 thread, ensuring a rigid, tilt-free connection. The camera side features the astrophotography standard M48 x 0.75 male thread, allowing you to connect a wide array of cameras from Canon, Nikon, Sony, Fuji, and more using a standard M48 T-ring. The adjustable nature of the flattener is critical for achieving the precise sensor-to-flattener distance required for a perfectly flat field with different camera models.\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 does \"1.0x power\" mean for the William Optics Flat73A?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA \u003cstrong\u003e1.0x flattener\u003c\/strong\u003e corrects for field curvature without changing the focal length or f-ratio of your telescope. With the Flat73A, your ZenithStar 73 will operate at its native focal length, producing images with the same scale and field of view as it would without the flattener, but with the benefit of sharp stars across the entire frame.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Flat73A flattener with a telescope other than the Z73?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, the Flat73A is optically and mechanically designed specifically for the William Optics ZenithStar 73. It uses a proprietary \u003cstrong\u003eM63 x 1 thread\u003c\/strong\u003e to attach to the Z73's focuser and its optical prescription is matched to that telescope's specific objective lens.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the maximum sensor size the Flat73A can illuminate and correct?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe William Optics Flat73A is designed to provide a corrected, unvignetted image circle for camera sensors up to \u003cstrong\u003efull-frame\u003c\/strong\u003e size. It is also perfectly suitable for smaller APS-C and Micro Four Thirds sensors.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I connect my Nikon Z mirrorless camera to the Flat73A?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYou will need an M48 T-ring specifically made for the Nikon Z-mount. The Flat73A provides the standard \u003cstrong\u003eM48 x 0.75 male thread\u003c\/strong\u003e that the T-ring will attach to. The adjustable mechanism on the flattener then allows you to set the correct distance to your camera's sensor for optimal correction.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow will the Flat73A improve my images of the North American Nebula (NGC 7000) with a Z73?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe ZenithStar 73 provides a wide field of view perfect for large targets like the North American Nebula (NGC 7000). However, without correction, stars at the edges of such a large object will appear elongated or out of focus. The Flat73A corrects this distortion, ensuring that every star across the vast nebula complex is rendered as a sharp, round point, resulting in a much cleaner and more professional final image.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Flat73A necessary if I'm only using an APS-C camera with my Z73?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, absolutely. While an APS-C sensor is smaller than full-frame, the field curvature of the Z73 is still significant enough to be visible on an APS-C chip. Using the Flat73A will provide a noticeably flatter field, which is critical for accurate guiding, clean image stacking, and producing high-quality images where the corner performance matches the center.\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\u003eFlattener Power\u003c\/td\u003e\n\u003ctd\u003e1.0 x\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Design\u003c\/td\u003e\n\u003ctd\u003e2 elements in 2 groups\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSupported Camera Formats\u003c\/td\u003e\n\u003ctd\u003eFull Frame, APS-C, M4\/3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTelescope Connection\u003c\/td\u003e\n\u003ctd\u003eM63 x 1 x 6 mm thread\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Connection\u003c\/td\u003e\n\u003ctd\u003eM48 x 0.75 x 4 mm thread\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSupported T-Mounts\u003c\/td\u003e\n\u003ctd\u003eCanon EF, RF, Nikon F, Z, Sony E, Pentax K, MFT (M4\/3), FUJI X\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTotal Optical Length\u003c\/td\u003e\n\u003ctd\u003e65.5 mm (Flattener 39.5 mm + Rotator\/Adapter 26 mm)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e328.8 g \/ 0.72 lbs\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\"\u003eWilliam Optics Adjustable Flat73A for Z73\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\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eNo downloads available for this product.\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\/william-optics-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eWilliam Optics 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":44967221657885,"sku":"WO-P-FLAT73A","price":384.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/WO-P-FLAT73A-1.jpg?v=1722098931"},{"product_id":"william-optics-adjustable-reducer-flattener-flat73r-for-z73","title":"William Optics Adjustable Reducer Flattener Flat73R for Z73","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eReduces focal length by a factor of 0.8x\u003c\/li\u003e\n\u003cli\u003eDesigned for the William Optics Zenithstar 73 telescope\u003c\/li\u003e\n\u003cli\u003eProvides edge-to-edge flat field for full-frame sensors\u003c\/li\u003e\n\u003cli\u003eConnects via a secure M63 x 1 thread\u003c\/li\u003e\n\u003cli\u003eFeatures a standard M48 x 0.75 camera thread\u003c\/li\u003e\n\u003cli\u003eIntegrated camera rotator for easy framing\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\u003eWilliam Optics Adjustable Reducer Flattener Flat73R for Z73\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Adjustable Reducer Flattener Flat73R is engineered specifically to transform the Zenithstar 73 APO refractor into a wide-field astrograph. Its 3-element, 3-group optical design delivers a 0.8x focal reduction, correcting for field curvature across full-frame sensors. The unit attaches via a robust M63 x 1 thread and presents a standard M48 x 0.75 T-mount to your camera, all while weighing just 573.9 g.\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\u003e0.8x Focal Reduction: A Wider, Faster Field for the Z73\u003c\/h3\u003e\n\u003cp\u003eThe core function of the Flat73R is its 0.8x reduction factor, which shortens the Z73's focal length for a significantly wider true field of view. This allows you to capture large targets like the Andromeda Galaxy (M31) or the entire Veil Nebula complex in a single frame. This reduction also concentrates incoming light, drastically shortening required exposure times and increasing your signal-to-noise ratio on faint deep-sky objects.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e3-Element, 3-Group Optics:\u003c\/strong\u003e This sophisticated design ensures high-contrast, sharp stars across the entire image circle, correcting for aberrations introduced by the reduction.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFull-Frame Illumination:\u003c\/strong\u003e The optics are designed to fully illuminate and flatten the field for sensors up to full-frame (36x24mm) format, preventing vignetting and distorted stars in the corners of your images.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eEngineered for the Z73: M63 Threads and an 89mm Optical Length\u003c\/h3\u003e\n\u003cp\u003eThe Flat73R provides a mechanically rigid connection to the Zenithstar 73. It threads directly onto the focuser's M63 x 1 thread, eliminating any potential for sag or flexure that can occur with compression fittings, especially with the added weight of a filter wheel and camera. The total optical length is 89 mm, composed of the 49 mm flattener body and a 40 mm rotator and adapter assembly that allows for precise framing of your target without loosening the camera.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSecure M63 Connection:\u003c\/strong\u003e Ensures perfect optical alignment and stability throughout an imaging session.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStandard M48 x 0.75 Camera Thread:\u003c\/strong\u003e Provides a wide, non-vignetting connection compatible with modern DSLR\/mirrorless T-rings and dedicated astronomy cameras.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIntegrated Rotator:\u003c\/strong\u003e The 40 mm adapter section includes a camera rotator, an essential feature for composing your shot without having to unthread your imaging train.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eZ73 Native vs. Reduced: What 0.8x Means for Your Images\u003c\/h3\u003e\n\u003cp\u003eWithout a corrector, the Z73 is a superb visual instrument, but for imaging, field curvature will soften stars at the edge of the frame. The Flat73R not only corrects this but fundamentally changes the telescope's imaging characteristics.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eWider Field of View:\u003c\/strong\u003e The 0.8x reduction allows you to fit larger celestial objects into your frame compared to imaging at the native focal length. This is critical for large nebulae and nearby galaxies.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFaster Imaging:\u003c\/strong\u003e By reducing the focal ratio, the Flat73R gathers the same amount of light in a shorter time. An object that requires a 10-minute exposure at the native focal length can be captured with similar signal in just over 6 minutes, allowing you to gather more data in a single night.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTrade-off:\u003c\/strong\u003e The primary trade-off is a slight reduction in image scale. For smaller targets like most galaxies or planetary nebulae, imaging at the native focal length (with a flattener-only accessory) will yield a larger, more detailed image.\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 does the William Optics Flat73R do for my Z73 telescope?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Flat73R is a dual-purpose optical accessory. It acts as a \u003cstrong\u003efield flattener\u003c\/strong\u003e to correct the natural curvature of the focal plane, ensuring sharp, point-like stars across your entire sensor, especially large full-frame chips. It also acts as a \u003cstrong\u003e0.8x focal reducer\u003c\/strong\u003e, which widens your field of view and makes the telescope \"faster,\" reducing your exposure times.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Flat73R compatible with my full-frame camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The William Optics Flat73R is designed to provide excellent correction and illumination for camera sensors up to and including the \u003cstrong\u003efull-frame (36x24mm)\u003c\/strong\u003e format. It provides a standard M48 x 0.75 thread for connection, which is ideal for minimizing vignetting with large sensors.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I attach my camera to the Flat73R reducer?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYou attach your camera via the Flat73R's \u003cstrong\u003eM48 x 0.75 T-mount thread\u003c\/strong\u003e. You will need an M48 T-ring specific to your camera's mount (e.g., Canon EF, Nikon F, Sony E). This provides a secure, threaded connection for your imaging train.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the Flat73R's weight of 573.9 g affect my Z73's balance?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, adding the \u003cstrong\u003e573.9 g (1.27 lbs)\u003c\/strong\u003e of the reducer, plus your camera and any other accessories, will require you to rebalance your telescope on the mount. The Z73's focuser is robust enough to handle the load, but proper balance in both RA and Dec is critical for accurate tracking.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I frame the entire North American Nebula (NGC 7000) with the Z73 and Flat73R?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The wide field of view provided by the 0.8x reduction is ideal for very large targets like the North American Nebula (NGC 7000) and the nearby Pelican Nebula (IC 5070). With most APS-C and full-frame cameras, you should be able to capture the entire nebula complex in a single frame.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy would I use the Z73 without the Flat73R reducer?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile the Flat73R is essential for wide-field imaging, you would remove it for visual observation with an eyepiece. For imaging smaller targets like the Whirlpool Galaxy (M51) or the Ring Nebula (M57), you might prefer to use a 1.0x flattener (sold separately) to maintain the telescope's native focal length for a larger image scale and more detail on the object.\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\u003eReducer Power\u003c\/td\u003e\n\u003ctd\u003e0.8x\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Design\u003c\/td\u003e\n\u003ctd\u003e3 Elements in 3 Groups\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Length\u003c\/td\u003e\n\u003ctd\u003eFlattener 49 mm + Rotator\/Adapter 40 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTelescope Connection\u003c\/td\u003e\n\u003ctd\u003eM63 x 1 (7 mm length)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Connection\u003c\/td\u003e\n\u003ctd\u003eM48 x 0.75 (4 mm length)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSensor Coverage\u003c\/td\u003e\n\u003ctd\u003eFull Frame, APS-C, M4\/3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Mount Support\u003c\/td\u003e\n\u003ctd\u003eCanon EF, RF, Nikon F, Z, Sony E, Pentax K, MFT (M4\/3), FUJI X\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e573.9 g \/ 1.27 lbs\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\/william-optics-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eWilliam Optics 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":44967221788957,"sku":"WO-P-FLAT73R","price":409.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/William-Optics-Adjustable-Reducer-Flattener-Flat73R-for-Z73-P-FLAT73R-1__40133.1596133243.1280.1280.jpg?v=1684339331"},{"product_id":"william-optics-x0-8-reducer-flattener-7a","title":"William Optics x0.8 Reducer Flattener 7A","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eReduces focal ratio by a factor of 0.8x\u003c\/li\u003e\n\u003cli\u003eTriplet lens design with 3 elements in 3 groups\u003c\/li\u003e\n\u003cli\u003eCorrects field curvature for full-frame sensors\u003c\/li\u003e\n\u003cli\u003eDesigned for specific William Optics GT102, FLT132, and GT153 refractors\u003c\/li\u003e\n\u003cli\u003eStandard M48 x 0.75 camera connection thread\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\u003eWilliam Optics x0.8 Reducer Flattener 7A\u003c\/h2\u003e\n\u003cp\u003eThe William Optics x0.8 Reducer Flattener 7A is an essential optical corrector engineered to convert select William Optics refractors into fast, wide-field astrographs. This unit reduces your telescope's focal length by a factor of 0.8x while its 3-element, 3-group triplet lens design delivers a perfectly flat field for full-frame camera sensors. It attaches via a robust M92 x 1 thread and requires 59.5 mm of back focus to achieve pinpoint stars across the entire image 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\u003eTriplet APO Optics: 0.8x Reduction for Full-Frame Sensors\u003c\/h3\u003e\n\u003cp\u003eThis corrector uses a three-element apochromatic lens structure to achieve its optical goals without introducing chromatic aberration. The 0.8x reduction factor effectively shortens your telescope's focal length, which provides a wider true field of view and reduces exposure times by nearly 40%. The flattener component corrects for the field curvature inherent in refractor optics, ensuring that stars in the corners of your full-frame or APS-C sensor are as sharp as those in the center.\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\u003eM92 Connection: Dedicated Fit for 3 William Optics Refractors\u003c\/h3\u003e\n\u003cp\u003eThe Flattener 7A is not a universal accessory; it is optically matched to specific William Optics telescopes to ensure optimal correction. It connects directly to the focuser drawtube using a secure M92 x 1 male thread. This corrector is designed exclusively for the Gran Turismo 102 (must have a 3\" focuser), the Fluorostar 132, and the Gran Turismo 153. This dedicated design guarantees that the flattener's corrective power is perfectly aligned with the optical characteristics of these premium refractors.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCamera Interface:\u003c\/strong\u003e The camera side features a standard M48 x 0.75 thread, providing a wide, unvignetted connection for filter wheels, off-axis guiders, and full-frame camera T-rings.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBack Focus:\u003c\/strong\u003e A precise back focus of 59.5 mm from the flattener's shoulder to the camera sensor is required. This distance must be maintained using extension tubes to achieve a flat field.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e At 888.4 g (1.96 lbs), it is a substantial optical element that requires a robust focuser to maintain collimation and prevent sag.\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\"\u003eWill the William Optics Flattener 7A work with my telescope?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis flattener is designed for a specific set of telescopes and will not work correctly with others. It is compatible \u003cstrong\u003eonly\u003c\/strong\u003e with the William Optics \u003cstrong\u003eGT102 (with 3\" focuser)\u003c\/strong\u003e, \u003cstrong\u003eFLT132\u003c\/strong\u003e, and \u003cstrong\u003eGT153\u003c\/strong\u003e. It connects via an M92 x 1 thread.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the required back focus for the Flattener 7A?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe required back focus is \u003cstrong\u003e59.5 mm\u003c\/strong\u003e. This is the distance from the shoulder of the M48 thread on the flattener to your camera's sensor plane. You must use the correct combination of spacers to achieve this distance for sharp, round stars across the field.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the 0.8x reduction affect my FLT132's imaging speed?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe FLT132 has a native focal ratio of f\/6.9. With the 0.8x reducer, the effective focal ratio becomes approximately f\/5.5. This \"faster\" system gathers light more quickly, allowing you to capture the same amount of signal on a target like the Heart Nebula (IC 1805) in significantly shorter exposure times.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use my full-frame camera with the William Optics Flattener 7A?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, the Flattener 7A is designed to fully illuminate and correct for full-frame sensors (24x36mm format). It also works perfectly with smaller APS-C and M4\/3 sensors. The camera connects via a standard M48 x 0.75 T-ring.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Flattener 7A suitable for imaging the Andromeda Galaxy (M31) with a GT153?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAbsolutely. The GT153 is a long focal length instrument. The 0.8x reduction provided by the Flattener 7A creates a wider field of view, making it much easier to frame large targets like the Andromeda Galaxy (M31) or the North American Nebula (NGC 7000) in their entirety.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does the \"3 Groups 3 Elements\" lens type mean for the Flattener 7A?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis refers to its optical design, which is a \u003cstrong\u003eTriplet\u003c\/strong\u003e. It uses three individual lens elements arranged in three groups. This sophisticated design allows it to reduce the focal length and flatten the field while maintaining excellent color correction (apochromatic performance), preventing bloated or blue-fringed stars.\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\u003eFlattener Power\u003c\/td\u003e\n\u003ctd\u003e0.8x\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLens Design\u003c\/td\u003e\n\u003ctd\u003e3 Elements in 3 Groups (Triplet)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSupported Camera Formats\u003c\/td\u003e\n\u003ctd\u003eFull Frame, APS-C, M4\/3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTelescope Connection\u003c\/td\u003e\n\u003ctd\u003eM92 x 1 x 6.5 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Connection\u003c\/td\u003e\n\u003ctd\u003eM48 x 0.75 x 4 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRequired Back Focus\u003c\/td\u003e\n\u003ctd\u003e59.5 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSupported T-Mounts\u003c\/td\u003e\n\u003ctd\u003eCanon EF, RF, Nikon F, Z, Sony E, Pentax K, MFT (M4\/3), FUJI X\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e888.4 g \/ 1.96 lbs\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\"\u003eWilliam Optics x0.8 Reducer Flattener 7A\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\/william-optics-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eWilliam Optics 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":44967223623965,"sku":"WO-P-FLAT7A","price":1087.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/products\/William-Optics-x0-8-Reducer-Flattener-7A-P-FLAT7A-1__75973.1596133243.1280.1280.jpg?v=1684339155"},{"product_id":"william-optics-wo-x0-72-reducer-flattener-8","title":"William Optics WO x0.72 Reducer Flattener 8","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eReduces focal ratio by a factor of 0.72x\u003c\/li\u003e\n\u003cli\u003eCorrects field curvature for full-frame sensors\u003c\/li\u003e\n\u003cli\u003e3-element, 3-group optical design\u003c\/li\u003e\n\u003cli\u003eConnects to telescope via M92 x 1 thread\u003c\/li\u003e\n\u003cli\u003eStandard M48 x 0.75 camera-side threading\u003c\/li\u003e\n\u003cli\u003eWeighs 1098 g (2.42 lbs)\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\u003eWilliam Optics WO x0.72 Reducer Flattener 8\u003c\/h2\u003e\n\u003cp\u003eThe William Optics WO x0.72 Reducer Flattener 8 is engineered to transform high-focal-length William Optics refractors into faster, wide-field astrographs capable of illuminating full-frame sensors. Its 3-element, 3-group design provides a 0.72x focal reduction, significantly decreasing exposure times while correcting for field curvature from edge to edge. This unit connects to the telescope focuser via a robust M92 x 1 thread and provides a standard M48 x 0.75 thread for direct attachment to modern DSLR and dedicated astronomy cameras.\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\u003eA Faster, Wider Field: 0.72x Reduction for Large Refractors\u003c\/h3\u003e\n\u003cp\u003eThe primary function of the Flattener 8 is to reduce your telescope's effective focal length by a factor of 0.72x. For an f\/7 refractor, this transforms the optical system into a faster f\/5.04 instrument, cutting required exposure times by nearly 50%. This speed advantage allows you to capture more data on faint targets in a single night and increases the field of view to frame large objects like the Andromeda Galaxy (M31) or the North American Nebula (NGC 7000).\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\u003eEdge-to-Edge Correction: Full-Frame Illumination with a 3-Element Design\u003c\/h3\u003e\n\u003cp\u003eDesigned specifically for large-aperture refractors, the Flattener 8 provides a corrected image circle that fully supports full-frame (36x24mm) camera sensors. The 3-element optical system in 3 groups is optimized to eliminate field curvature and minimize off-axis aberrations, ensuring that stars remain tight, pinpoint sources across the entire frame. This avoids the bloated, comatic stars in the corners that are common in uncorrected systems, delivering professional-grade astrophotography results.\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\u003eRobust Integration: M92 Telescope Thread and M48 Camera Support\u003c\/h3\u003e\n\u003cp\u003eThe Flattener 8 is built for a secure, flex-free imaging train. It attaches to compatible William Optics focusers using a large M92 x 1 male thread for a rigid connection. On the camera side, it terminates in a standard M48 x 0.75 male thread, the ideal interface for connecting filter wheels, off-axis guiders, and a wide range of camera-specific T-rings. At 1098 g (2.42 lbs), its solid construction ensures optical alignment is maintained, though it requires a robust focuser to handle the load.\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\"\u003eWhich William Optics telescopes are compatible with the Flattener 8?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Flattener 8 is designed for William Optics' larger refractors that feature a focuser with a female M92 x 1 thread. It is commonly paired with models like the Fluorostar 132 (FLT132) and Fluorostar 156 (FLT156). Always confirm your telescope's focuser thread before purchasing.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDoes the WO Flattener 8 provide a fully corrected field for a full-frame sensor?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, it is explicitly designed to provide excellent correction and illumination for \u003cstrong\u003efull-frame sensors (36x24mm)\u003c\/strong\u003e, as well as smaller APS-C and M4\/3 formats. You can expect sharp, pinpoint stars from the center to the corners of your full-frame camera.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the 0.72x reduction of the Flattener 8 affect my imaging time?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eFocal reduction makes your telescope \"faster\" by concentrating the same amount of light onto a smaller area. A 0.72x reducer shortens exposure times by a factor of (0.72)^2, or approximately 0.52. This means a 10-minute exposure without the reducer would require only about 5 minutes to achieve the same signal-to-noise ratio with the Flattener 8 installed.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the required back focus for the William Optics Flattener 8?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile the optical length is 77 mm, the required back focus (the distance from the flattener's rear flange to the camera sensor) is a critical, fixed distance that must be precisely met. This specification is typically 55mm for M48-threaded correctors but you must consult the documentation for your specific William Optics telescope and this flattener to confirm the exact spacing needed for optimal performance.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat are the connection threads on the WO Flattener 8?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Flattener 8 uses two primary threads:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eTelescope Side:\u003c\/strong\u003e M92 x 1 male thread.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCamera Side:\u003c\/strong\u003e M48 x 0.75 male thread (also known as the 2\" filter thread standard).\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the 1098 g weight of the Flattener 8 a concern for my telescope's focuser?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAt 2.42 lbs, the Flattener 8 is a substantial piece of optical equipment. It requires a high-quality, robust focuser capable of handling heavy imaging trains without slipping or flexing. The rack-and-pinion focusers found on the William Optics telescopes it's designed for are more than capable of supporting this weight along with a camera.\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\u003eReducer Power\u003c\/td\u003e\n\u003ctd\u003e0.72x\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Design\u003c\/td\u003e\n\u003ctd\u003e3 Elements in 3 Groups\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Format Support\u003c\/td\u003e\n\u003ctd\u003eFull Frame, APS-C, M4\/3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTelescope Connection\u003c\/td\u003e\n\u003ctd\u003eM92 x 1 x 7.5 mm Thread\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Connection\u003c\/td\u003e\n\u003ctd\u003eM48 x 0.75 x 4 mm Thread\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSupported T-Mounts\u003c\/td\u003e\n\u003ctd\u003eCanon EF, RF; Nikon F, Z; Sony E; Pentax K; MFT (M4\/3); FUJI X\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Length\u003c\/td\u003e\n\u003ctd\u003e77 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e1098 g \/ 2.42 lbs\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\"\u003eWilliam Optics WO x0.72 Reducer Flattener 8\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\/william-optics-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eWilliam Optics 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":44967224148253,"sku":"WO-P-FLAT8","price":1161.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/William-Optics-WO-x0-72-Reducer-Flattener-8-P-FLAT8-1__56697.1596133245.1280.1280.jpg?v=1684339346"},{"product_id":"william-optics-adjustable-flat6aiii-for-flt91","title":"William Optics Adjustable Flat6AIII for FLT91","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eDedicated Field Flattener for the William Optics FLT91 Telescope\u003c\/li\u003e\n\u003cli\u003eCorrects Field Curvature for Pinpoint Stars Edge-to-Edge\u003c\/li\u003e\n\u003cli\u003eIntegrated Adjustment Ring for Precise Back Focus Tuning\u003c\/li\u003e\n\u003cli\u003eIncludes Custom Adapter for a Secure Connection to the FLT91\u003c\/li\u003e\n\u003cli\u003eEnables Full-Frame Astrophotography with the FLT91\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\u003eDownloads\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\u003eWilliam Optics Adjustable Flat6AIII for FLT91\u003c\/h2\u003e\n\u003cp\u003eOwners of the William Optics Fluorostar 91 refractor can achieve a perfectly flat photographic field with the dedicated Adjustable Flat6AIII corrector. This optical system is engineered specifically for the FLT91 to eliminate field curvature, rendering stars as sharp, pinpoint sources from the center to the very edge of the frame. The package includes the Flat6AIII flattener and the specific adapter ring for a seamless, rigid connection, with an integrated adjustment mechanism for precise back focus control.\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\u003eAchieve a Perfectly Flat Field with the FLT91\u003c\/h3\u003e\n\u003cp\u003eWhile the FLT91 provides exceptional color correction, like all fast refractors, its native focal plane has a slight curvature. For visual use, this is unnoticeable, but for astrophotography, it results in slightly elongated stars in the corners of an image. The Flat6AIII is the matched solution, designed to counteract this specific optical characteristic, ensuring your images have a professional, uniformly sharp appearance across even large full-frame sensors.\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\u003eIntegrated Adjustment for a Versatile Imaging Train\u003c\/h3\u003e\n\u003cp\u003eThe \"Adjustable\" design of the Flat6AIII is its key mechanical advantage. It features a built-in, rotatable adjustment ring that allows you to dial in the perfect sensor-to-flattener distance for your specific camera, filter wheel, or off-axis guider setup. This eliminates the trial-and-error of finding the right combination of extension tubes and spacers, saving you valuable time in the field. This unit ships with the necessary adapter ring, ensuring a direct, secure, and perfectly centered attachment to the FLT91's focuser drawtube for a completely rigid imaging train.\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 William Optics Adjustable Flat6AIII for the FLT91?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003eWilliam Optics Adjustable Flat6AIII\u003c\/strong\u003e is a dedicated field flattener designed for the FLT91 apo refractor. Its primary function is to correct for the natural field curvature of the telescope's optics, ensuring that stars are sharp and pinpoint across the entire image sensor, from the center to the corners.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy is the \"adjustable\" feature of the Flat6AIII important for my FLT91 setup?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe adjustable mechanism allows you to precisely set the back focus distance between the flattener's optics and your camera's sensor. This is critical because different cameras, filter wheels, and off-axis guiders create different optical path lengths. The adjustability ensures you can achieve perfect correction with your specific imaging train without needing a collection of separate spacers.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDo I need a separate adapter to connect the Flat6AIII to my William Optics FLT91?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo. This product package includes both the Flat6AIII flattener and the specific adapter ring required for a direct and secure connection to the William Optics FLT91 telescope's focuser.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the Adjustable Flat6AIII help when imaging large targets like the Andromeda Galaxy (M31) with the FLT91?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhen imaging a large object like the Andromeda Galaxy (M31), you want the entire field to be perfect. Without the \u003cstrong\u003eFlat6AIII\u003c\/strong\u003e, the stars at the edges of the galaxy might appear soft or elongated. By flattening the field, this corrector ensures that every star in your frame is a sharp point, resulting in a much more professional and aesthetically pleasing final image.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Flat6AIII a focal reducer as well as a flattener?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe primary design function of the Flat6AIII is field flattening. While some flatteners also offer focal reduction, this model is specified as a 1.0x flattener, meaning it is designed to correct aberrations without changing the native focal length or f-ratio of the FLT91 telescope.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the Adjustable Flat6AIII for FLT91 work with both DSLR and dedicated astronomy cameras?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The adjustable back focus is specifically designed to accommodate the different flange distances of various cameras. Whether you are using a DSLR with a standard T-ring or a dedicated cooled astronomy camera with a filter wheel, you can tune the spacing for optimal optical performance.\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\u003eProduct Name\u003c\/td\u003e\n\u003ctd\u003eWilliam Optics Adjustable Flat6AIII for FLT91\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompatibility\u003c\/td\u003e\n\u003ctd\u003eWilliam Optics FLT91 Apochromatic Refractor\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePrimary Function\u003c\/td\u003e\n\u003ctd\u003eField Flattener (1.0x)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eKey Feature\u003c\/td\u003e\n\u003ctd\u003eIntegrated Adjustable Back Focus\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eConnection\u003c\/td\u003e\n\u003ctd\u003eIncludes dedicated adapter for FLT91 focuser\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\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/william-optics-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eWilliam Optics 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":44967782187293,"sku":"WO-P-FLAT6AIII-M92","price":480.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/William-Optics-Adjustable-Flat6AIII-P-FLAT6AIII-1__21819.1596133240.1280.1280__76625.1614355641.1280.1280.jpg?v=1684345861"},{"product_id":"william-optics-p-flat-132","title":"William Optics Ultra Flat 132 (0.79x Reducer)","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eReduces focal ratio by a factor of 0.79x\u003c\/li\u003e\n\u003cli\u003eProvides a flat field for Full Frame, APS-C, and M4\/3 sensors\u003c\/li\u003e\n\u003cli\u003e3-element, 3-group optical design\u003c\/li\u003e\n\u003cli\u003eConnects to telescope via M92 thread\u003c\/li\u003e\n\u003cli\u003eConnects to camera train via M54 thread\u003c\/li\u003e\n\u003cli\u003eWeighs 2.42 lbs (1096 g)\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\u003eUltra Flat 132 (0.79x Reducer)\u003c\/h2\u003e\n\u003cp\u003eThe Ultra Flat 132 (0.79x Reducer) is the dedicated optical corrector for the William Optics Fluorostar 132, transforming the telescope into a faster, wider astrograph. This corrector provides a 0.79x focal reduction and flattens the image field for sensors up to full-frame format. Its 3-element, 3-group lens design ensures sharp stars across the entire frame, while the robust M92 telescope-side thread and 2.42 lb weight guarantee a rigid, flex-free imaging train.\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\u003e0.79x Reduction: Transform Your FLT132 into an f\/5.45 Astrograph\u003c\/h3\u003e\n\u003cp\u003eBy applying a 0.79x reduction factor, this flattener-reducer converts the FLT132's native f\/6.9 focal ratio to a significantly faster f\/5.45. This speed increase allows you to capture the same amount of signal in nearly half the time, dramatically improving efficiency during short imaging nights. The corresponding wider field of view lets you frame large celestial targets, such as the Andromeda Galaxy (M31) or the Veil Nebula complex, in a single shot.\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\u003e3-Element, 3-Group Design: A Flat Field for Full-Frame Sensors\u003c\/h3\u003e\n\u003cp\u003eEngineered to correct for field curvature, this unit ensures your images have pinpoint stars from the center to the corners of the sensor. The 3-element, 3-group optical formula is optimized to provide a corrected image circle large enough for full-frame cameras, as well as smaller APS-C and M4\/3 formats. This eliminates the frustration of elongated stars at the edge of the field, a critical requirement for producing high-quality astrophotographs.\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\u003eM92 \u0026amp; M54 Threads: 137.5mm of Precisely Corrected Optical Path\u003c\/h3\u003e\n\u003cp\u003eThe Ultra Flat 132 ensures a secure, perfectly aligned connection to your imaging train. It attaches directly to the FLT132 focuser via a male M92 x 1 thread, preventing tilt or sag. The camera side features a standard M54 x 0.75 female thread, providing a solid interface for filter wheels, off-axis guiders, and cameras. For optimal optical correction, the total distance from the reducer's M54 shoulder to the camera sensor must be precisely set, accounting for the unit's 137.5 mm optical length.\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\u003eNative f\/6.9 vs. Reduced f\/5.45: Choosing the Right Focal Length\u003c\/h3\u003e\n\u003cp\u003eDeciding whether to image with the Ultra Flat 132 reducer depends entirely on your target. While the reducer offers significant advantages in speed and field of view, the native focal length of the telescope retains its own utility.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eNative f\/6.9 Imaging:\u003c\/strong\u003e The telescope's native focal length provides higher magnification and resolution. This is ideal for smaller targets like the Whirlpool Galaxy (M51), the Ring Nebula (M57), or planetary details where image scale is more important than field of view.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReduced f\/5.45 Imaging:\u003c\/strong\u003e The 0.79x reducer provides a wider field and cuts exposure times nearly in half. This is the clear choice for large emission nebulae like the North American Nebula (NGC 7000) or for creating mosaics of the Milky Way's core.\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 back focus is required for the Ultra Flat 132 reducer?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Ultra Flat 132 reducer has a specified \u003cstrong\u003eoptical length of 137.5 mm\u003c\/strong\u003e. This is the total distance required from the reducer's M54 thread shoulder to the camera sensor for optimal field correction. You must account for the optical path length of any filters, adapters, and the camera's own internal back focus to achieve this precise spacing.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Ultra Flat 132 compatible with telescopes other than the William Optics Fluorostar 132?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo. This reducer is optically designed and mechanically threaded specifically for the William Optics Fluorostar 132 telescope. Its \u003cstrong\u003eM92 x 1 telescope thread\u003c\/strong\u003e and corrective optics are matched to that telescope's specific focal length and optical characteristics. Using it on other telescopes will not produce a corrected image.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the 0.79x reduction of the Ultra Flat 132 affect my exposure times?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003e0.79x\u003c\/strong\u003e reduction makes the telescope optically faster, reducing the required exposure time for a given signal level. An f\/6.9 system becomes f\/5.45, which gathers light approximately 1.6 times faster. This means an 8-minute sub-exposure at the native focal length can be achieved in about 5 minutes with the reducer.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the Ultra Flat 132 reducer fully illuminate my full-frame camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The Ultra Flat 132 is designed to provide a corrected and illuminated image circle that covers \u003cstrong\u003eFull Frame, APS-C, and M4\/3\u003c\/strong\u003e sensors. You can use it with large-format astronomy cameras or full-frame DSLRs\/mirrorless cameras without significant vignetting or distorted stars in the corners.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the Ultra Flat 132 reducer help when imaging the Andromeda Galaxy (M31) with an FLT132?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Andromeda Galaxy is a very large target. At the native focal length of the FLT132, you can only capture its bright core. The \u003cstrong\u003e0.79x reducer\u003c\/strong\u003e widens the field of view enough to frame the entire galaxy, including its faint outer arms and companion galaxies M32 and M110, in a single shot with a full-frame sensor.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI'm using an M54 filter wheel with the Ultra Flat 132 reducer. How do I achieve the correct spacing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003eM54 x 0.75\u003c\/strong\u003e camera-side thread is your starting point. You need to calculate the total length of your imaging train (filter wheel thickness, camera sensor depth, any off-axis guider) and add M54 spacers as needed to reach the total required \u003cstrong\u003e137.5 mm optical length\u003c\/strong\u003e. Remember to account for the 1\/3 optical path addition for any glass filters in the light path.\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\u003eFlattener Power\u003c\/td\u003e\n\u003ctd\u003e0.79x\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Format\u003c\/td\u003e\n\u003ctd\u003eFull Frame, APS-C, M4\/3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLens Design\u003c\/td\u003e\n\u003ctd\u003e3 Elements in 3 Groups\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Length\u003c\/td\u003e\n\u003ctd\u003e137.5 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTelescope Thread\u003c\/td\u003e\n\u003ctd\u003eM92 x 1 x 6.5 mm (Male)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Thread\u003c\/td\u003e\n\u003ctd\u003eM54 x 0.75 x 4 mm (Female)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e1096 g \/ 2.42 lbs\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\"\u003eUltra Flat 132 (0.79x Reducer)\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\/william-optics-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eWilliam Optics 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":52853690695965,"sku":"WO-P-FLAT-132","price":1474.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/WilliamOptics-Ultra-Flat-132-0-79x-Reducer-1_ffef41c7-3bfa-4948-8ce7-5113ff2d4fa0.jpg?v=1788457808"},{"product_id":"william-optics-p-flat-156","title":"William Optics Ultra Flat 156 (0.79x Reducer)","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eReduces focal ratio by a factor of 0.79x\u003c\/li\u003e\n\u003cli\u003eDesigned for Medium Format, Full Frame, and APS-C sensors\u003c\/li\u003e\n\u003cli\u003e3-element, 3-group optical design\u003c\/li\u003e\n\u003cli\u003eRequires 75.5mm of optical length (back focus)\u003c\/li\u003e\n\u003cli\u003eConnects to focusers via an M92 x 1 thread\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\u003eUltra Flat 156 (0.79x Reducer)\u003c\/h2\u003e\n\u003cp\u003eThe Ultra Flat 156 reducer shortens your telescope's focal length by a factor of 0.79x, using a 3-element, 3-group optical design to deliver wider fields of view for sensors up to Medium Format. It establishes a precise 75.5mm optical length from its M54 camera-side thread and connects to the focuser via a robust M92 x 1 thread. Weighing 1202 g (2.65 lbs), this reducer is built to support large, modern CMOS and CCD cameras without flexure.\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\u003e0.79x Reduction: Faster Imaging and Wider Fields of View\u003c\/h3\u003e\n\u003cp\u003eThis reducer transforms your telescope's imaging characteristics by reducing its effective focal length. A 0.79x reduction factor not only expands your field of view to capture larger celestial objects but also accelerates your imaging sessions. By concentrating the same amount of light onto a smaller area, it effectively makes your telescope faster, allowing you to gather more signal in less time.\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\u003e3-Element Design: A Flat Field for Medium Format and Larger Sensors\u003c\/h3\u003e\n\u003cp\u003eEngineered with a 3-element optical formula arranged in 3 distinct groups, the Ultra Flat 156 is designed to deliver a flat, well-corrected image plane across very large sensors. It provides full illumination for Medium Format, Full Frame, APS-C, and M4\/3 camera formats. This ensures that you can utilize the full potential of modern, large-format astronomy cameras, achieving sharp, pinpoint stars from the center to the corners of your 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\u003eMechanical Integration: M92 Threads and 75.5mm Optical Length\u003c\/h3\u003e\n\u003cp\u003eThe Ultra Flat 156 is designed for robust, threaded connections within the imaging train. It features an M92 x 1 male thread for attachment to a compatible focuser and an M54 x 0.75 male thread on the camera side. Achieving critical focus requires a precise optical length of 75.5mm from the reducer's shoulder to the camera sensor. At 2.65 lbs (1202 g), its substantial build demands a high-capacity focuser and careful attention to mount balancing.\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 primary function of the Ultra Flat 156 reducer?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Ultra Flat 156 serves two main purposes: it reduces your telescope's focal length by a factor of \u003cstrong\u003e0.79x\u003c\/strong\u003e, which provides a wider field of view, and it flattens the image plane to ensure sharp stars across large camera sensors.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat cameras are compatible with the Ultra Flat 156 reducer?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis reducer is designed to illuminate a wide range of sensor sizes, including \u003cstrong\u003eMedium Format, Full Frame, APS-C, and M4\/3\u003c\/strong\u003e. It connects to the camera or filter wheel via a standard \u003cstrong\u003eM54 x 0.75\u003c\/strong\u003e male thread.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I achieve the correct 75.5mm spacing for the Ultra Flat 156?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe required \u003cstrong\u003e75.5mm optical length\u003c\/strong\u003e, or back focus, is measured from the shoulder of the reducer's M54 thread to your camera's sensor. You will need to use a combination of M54 extension rings and adapters to precisely match this distance for your specific camera setup.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat kind of telescope focuser does the Ultra Flat 156 connect to?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Ultra Flat 156 features an \u003cstrong\u003eM92 x 1\u003c\/strong\u003e male thread on the telescope side. It is designed to thread directly into a focuser drawtube with a matching M92 female thread for a secure, tilt-free connection.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI have a full-frame camera like a ZWO ASI6200MM. Will the Ultra Flat 156 fully illuminate its sensor?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The Ultra Flat 156 is specified to cover sensors up to \u003cstrong\u003eMedium Format\u003c\/strong\u003e, which is larger than the sensor in a full-frame camera. It will provide a flat, well-corrected, and fully illuminated field for your full-frame camera, ensuring no vignetting or distorted stars at the edges.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eGiven its 2.65 lbs weight, what should I consider when adding the Ultra Flat 156 to my setup?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe significant weight of \u003cstrong\u003e1202 g (2.65 lbs)\u003c\/strong\u003e requires careful consideration. First, ensure your focuser can handle the load without slipping or tilting. Second, you will need to re-balance your telescope on the mount after installing the reducer and camera to prevent tracking errors and strain on the motors.\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\u003eFlattener Power\u003c\/td\u003e\n\u003ctd\u003e0.79 x\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLens Type\u003c\/td\u003e\n\u003ctd\u003e3 Groups 3 Elements\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Format Compatibility\u003c\/td\u003e\n\u003ctd\u003eMedium Format, Full Frame, APS-C, M4\/3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Length (Back Focus)\u003c\/td\u003e\n\u003ctd\u003e75.5 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTelescope Side Thread\u003c\/td\u003e\n\u003ctd\u003eM92 x 1 x 6.5 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera Side Thread\u003c\/td\u003e\n\u003ctd\u003eM54 x 0.75 x 4 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e1202 g \/ 2.65 lbs\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\u003cp\u003eWarranty information for this product is not available.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":52853690761501,"sku":"WO-P-FLAT-156","price":1474.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/WilliamOptics-Ultra-Flat-156-0-79x-Reducer-1_3261d2a8-0892-45a4-b3d2-bc9c9e63c550.jpg?v=1788457819"}],"url":"https:\/\/davidastro.com\/collections\/william-optics-field-flatteners-reducers-and-coma-correctors.oembed","provider":"David Astro","version":"1.0","type":"link"}