{"title":"William Optics Zenithstar APO Refractors","description":"\u003cp\u003eWilliam Optics Zenithstar refractors are compact apochromatic doublets for portable astrophotography and visual observing. This collection includes the Zenithstar 61II APO, a small travel scope, and the Zenithstar 81 WIFD with internal focusing.\u003c\/p\u003e\u003cp\u003eDedicated correctors are also here: the adjustable Flat61 flattener and Flat61R reducer flattener for the Z61, and the Flat73A flattener and Flat73R reducer flattener for the Z73, which let you choose between native and reduced focal length.\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-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-zenithstar-61ii-apo","title":"William Optics Zenithstar 61II APO","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e61mm Aperture Apochromatic Doublet Refractor\u003c\/li\u003e\n\u003cli\u003eOhara FPL-53 ED Glass Element\u003c\/li\u003e\n\u003cli\u003eFast f\/5.9 Focal Ratio for Wide-Field Imaging\u003c\/li\u003e\n\u003cli\u003eIncludes Flat61A Field Flattener\u003c\/li\u003e\n\u003cli\u003e2-inch Dual-Speed Rack \u0026amp; Pinion Focuser\u003c\/li\u003e\n\u003cli\u003eIntegrated Bahtinov Mask in Lens Cap\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 Zenithstar 61II APO Refractor\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Zenithstar 61II APO packages a color-free FPL-53 glass doublet and a precise 2-inch dual-speed focuser into a compact, portable optical tube. Designed as a complete wide-field imaging solution, this f\/5.9 refractor includes the essential Flat61A field flattener, delivering an instrument ready for demanding astrophotography right out of its included soft case.\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\u003eFPL-53 APO Doublet for Apochromatic Imaging\u003c\/h3\u003e\n\u003cp\u003eAt the core of the Zenithstar 61II is an air-spaced doublet objective featuring a genuine Ohara FPL-53 ED glass element. This apochromatic design virtually eliminates chromatic aberration, ensuring stars are rendered as sharp, high-contrast points of light without distracting purple fringing. The result is cleaner raw data with truer color fidelity, whether you're imaging emission nebulae or capturing the subtle hues in a star cluster.\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\u003eField-Ready Portability and CNC Mechanicals\u003c\/h3\u003e\n\u003cp\u003eEngineered for the traveling imager, the Z61II is built from CNC-machined aluminum for a rigid yet lightweight frame that holds collimation. The scope includes a Vixen-style dovetail for compatibility with a wide range of popular mounts, and a unique saddle handle bar that simplifies transport while also serving as a mounting point for guide scopes or other accessories. A custom-fit soft carrying case protects the instrument during travel to your favorite dark-sky site.\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\u003eImaging-Ready with a 2-Inch Focuser and Flat61A Flattener\u003c\/h3\u003e\n\u003cp\u003eWilliam Optics delivers the Z61II as a complete imaging system, not just an optical tube. The 2-inch dual-speed focuser provides the fine adjustment needed for critical focus, a process made simple by the Bahtinov mask cleverly integrated into the lens cap. Crucially, the package includes the matched Flat61A field flattener, which corrects for field curvature to ensure your images have sharp, pinpoint stars from the center to the corners of the frame—an essential component often sold separately.\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\"\u003eIs the William Optics Zenithstar 61II ready for astrophotography out of the box?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003e\u003cstrong\u003eYes.\u003c\/strong\u003e The Zenithstar 61II is packaged as a complete imaging solution. It includes the essential \u003cstrong\u003eFlat61A field flattener\u003c\/strong\u003e to ensure sharp stars across your sensor, a precise \u003cstrong\u003e2-inch dual-speed focuser\u003c\/strong\u003e for accurate adjustments, and an integrated \u003cstrong\u003eBahtinov mask\u003c\/strong\u003e in the lens cap for achieving critical focus easily.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the FPL-53 glass in the Zenithstar 61II benefit imaging?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Ohara \u003cstrong\u003eFPL-53 ED glass\u003c\/strong\u003e element provides apochromatic (APO) color correction. This minimizes chromatic aberration, or false color, which can appear as purple halos around bright stars. For imagers, this means sharper stars, higher contrast, and more accurate color data directly from the camera.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat makes the Zenithstar 61II a good portable or travel telescope?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Z61II is designed for portability. Its compact size, lightweight CNC-machined aluminum body, and included padded soft carrying case make it easy to transport. It's an ideal \"grab-and-go\" scope for taking to dark sky sites or on trips.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would the Zenithstar 61II frame a large target like the North American Nebula (NGC 7000)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Zenithstar 61II's wide field of view is perfectly suited for large deep-sky objects. When paired with a camera using an APS-C or smaller sensor, it can easily capture the entirety of massive targets like the North American Nebula (NGC 7000) or the Andromeda Galaxy (M31) in a single frame.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Zenithstar 61II for visual observing on a small tracking mount?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAbsolutely. While optimized for imaging, the Z61II is also an excellent visual instrument. Its light weight and Vixen dovetail make it a perfect match for portable tracking mounts like the Sky-Watcher Star Adventurer. With a 2-inch diagonal and a low-power, wide-field eyepiece, it provides stunning, expansive views of the Milky Way.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the purpose of the saddle handle bar on the Zenithstar 61II?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe handle bar serves two functions. It provides a secure and balanced grip for carrying the telescope and placing it on a mount. It also features a Vixen-style saddle, allowing you to mount accessories like a small guide scope or a red dot finder directly on top of the optical tube.\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\u003eAvailable Options\u003c\/td\u003e\n\u003ctd\u003eGrey, Gold\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\"\u003eZenithstar 61 II APO OTA\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eFlat61A Field Flattener\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eMounting Rings with Saddle Handle Bar\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eVixen-Style Dovetail Bar\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eLens Cap with Integrated Bahtinov Mask\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eSoft Carrying Case\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\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":"Grey","offer_id":44967230898461,"sku":"WO-A-Z61IITG","price":962.0,"currency_code":"CAD","in_stock":true},{"title":"Gold","offer_id":51501958594845,"sku":"WO-A-Z61IIGD","price":962.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/WO-Z-61-II-Grey-1.jpg?v=1722104068"},{"product_id":"william-optics-zenithstar-81-wifd-telescope","title":"William Optics Zenithstar 81 WIFD Telescope","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003ePatented William Optics Internal Focus Design (WIFD)\u003c\/li\u003e\n\u003cli\u003eRigid M92 Rear Thread with M63 Adapter Included\u003c\/li\u003e\n\u003cli\u003eVixen\/Arca-Swiss Dual-Sided Mounting Plate\u003c\/li\u003e\n\u003cli\u003eIntegrated Handle Bar and Mounting Rings\u003c\/li\u003e\n\u003cli\u003eSoft Padded Carry Case for Transport and Storage\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 Zenithstar 81 WIFD Telescope\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Zenithstar 81 WIFD Telescope delivers exceptional optical stability for astrophotography by eliminating drawtube sag with its patented internal focusing mechanism. The robust rear M92 thread, which converts to M63 with the included adapter, provides a solid, flex-free connection for heavy cameras and complex imaging trains.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe Patented WIFD: A Revolution in Internal Focusing\u003c\/h3\u003e\n\u003cp\u003eWilliam Optics' innovative Internal Focus Design (WIFD) is the centerpiece of the Zenithstar 81. Unlike traditional focusers that move an external drawtube, the WIFD moves the optics internally, ensuring the camera and other accessories remain fixed. This design completely prevents the image shift and tilt that can ruin long exposures, especially when using heavy filter wheels or off-axis guiders.\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\u003eAstrophotography-Ready Mechanics from Case to Mount\u003c\/h3\u003e\n\u003cp\u003eThis telescope is engineered for immediate use in the field. It arrives with a pre-installed dual-side mounting plate compatible with both Vixen-style and Arca-Swiss saddles, offering broad mount compatibility. The package also includes a sturdy mounting ring, a combination handle bar and guidescope saddle, and a high-quality soft carry case for safe transport to your dark-sky site.\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\u003eAn Expandable Optical System for Reducers and Guiders\u003c\/h3\u003e\n\u003cp\u003eThe Zenithstar 81 WIFD is designed as the core of a flexible imaging system. While its native optics provide sharp, high-contrast views, it is fully compatible with optional accessories like the Flat6aIII focal reducer for a wider field of view. The integrated handle bar also serves as a saddle for the optional UniGuide series of guidescopes, creating a compact and rigid platform for precise tracking during long-exposure astrophotography.\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 main advantage of the Zenithstar 81 WIFD's internal focuser?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe primary advantage of the \u003cstrong\u003eWilliam Optics Internal Focus Design (WIFD)\u003c\/strong\u003e is the elimination of focuser sag and tilt. By moving the optics internally and keeping the camera stationary, it provides a completely rigid imaging train that maintains perfect optical alignment, which is critical for sharp stars edge-to-edge when using heavy cameras and accessories.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Zenithstar 81 WIFD with my existing Vixen-style mount?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The Zenithstar 81 WIFD includes a dual-sided mounting plate that is compatible with both \u003cstrong\u003eVixen-style\u003c\/strong\u003e and \u003cstrong\u003eArca-Swiss\u003c\/strong\u003e saddles, allowing you to attach it to a wide variety of astronomical mounts and camera tripods without needing to purchase additional hardware.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat do I need to start guiding the Zenithstar 81 WIFD for long exposures on the Andromeda Galaxy (M31)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eTo guide the Zenithstar 81 WIFD, you will need a guidescope, such as the optional William Optics UniGuide, and a guide camera. The telescope's integrated handle bar is designed to mount a guidescope directly, creating a solid, parallel setup for accurate tracking of celestial objects like the Andromeda Galaxy (M31).\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDoes the Zenithstar 81 WIFD come with everything I need to attach it to a mount?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, the package includes the essential mounting hardware. It comes with a mounting ring and a dual-sided Vixen\/Arca-Swiss plate, allowing you to secure it to most common astronomical mounts right out of the box.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the internal focuser on the Zenithstar 81 WIFD handle heavy imaging trains?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe internal focuser is exceptionally well-suited for heavy imaging trains. Because the camera and accessories are threaded directly to the rigid M92 rear port of the telescope tube, their weight is not supported by a moving drawtube. This design prevents flexure, ensuring the sensor remains perfectly orthogonal to the light path regardless of the setup's weight or orientation.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the purpose of the included M92 to M63 adapter for the Zenithstar 81 WIFD?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Zenithstar 81 WIFD features a large M92 native rear thread for maximum stability. The included \u003cstrong\u003eM92 to M63 adapter\u003c\/strong\u003e allows you to connect a wide range of accessories, including many field flatteners and reducers that use the more common M63 thread standard, providing greater flexibility for building your imaging train.\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\u003eAvailable Options\u003c\/td\u003e\n\u003ctd\u003eGold, Red\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\"\u003eMain Tube\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eBahtinov Cap\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eM92→M63 Adapter\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eDual-side Plate\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eMounting Ring \u0026amp; Handle bar\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eSoft Carry Case\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eAllen Key Set\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":"Gold","offer_id":51292718235933,"sku":"WO-T-ZS-81GD-WIFD","price":1515.0,"currency_code":"CAD","in_stock":true},{"title":"Red","offer_id":51292718203165,"sku":"WO-T-ZS-81RD-WIFD","price":1398.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Z-81-WIFD-perspective-gold.jpg?v=1779207603"}],"url":"https:\/\/davidastro.com\/collections\/william-optics-zenithstar-apo-refractors.oembed","provider":"David Astro","version":"1.0","type":"link"}