{"title":"William Optics Fluorostar FLT APO Refractors","description":"\u003cp\u003eWilliam Optics Fluorostar FLT refractors are triplet apochromats aimed at serious deep-sky imaging and high-contrast visual use. The line includes the Fluorostar 91, 120, 132 and 156.\u003c\/p\u003e\u003cp\u003eMatching correctors are part of the collection: the adjustable Flat6AIII for the FLT91, and the Ultra Flat 132 and Ultra Flat 156, both 0.79x reducers that flatten the field and shorten the focal length for faster exposures on these larger tubes.\u003c\/p\u003e","products":[{"product_id":"william-optics-fluorostar-132","title":"William Optics Fluorostar 132","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e132mm Aperture, 910mm Focal Length (f\/6.9)\u003c\/li\u003e\n\u003cli\u003eAir-Spaced Triplet Apochromatic Objective\u003c\/li\u003e\n\u003cli\u003ePremium FPL-53 Glass for Superior Color Correction\u003c\/li\u003e\n\u003cli\u003eHeavy-Duty 3.7\" Rack \u0026amp; Pinion Focuser\u003c\/li\u003e\n\u003cli\u003e360° Rotatable Focuser for Easy Framing\u003c\/li\u003e\n\u003cli\u003eFully CNC-Machined Aluminum Tube\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 Fluorostar 132 APO Refractor\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Fluorostar 132 combines a 132mm aperture with a 910mm focal length (f\/6.9) to serve as a premier instrument for high-resolution astrophotography and critical visual observation. Its air-spaced triplet objective lens uses premium FPL-53 glass to achieve apochromatic correction, while the massive 3.7-inch Rack \u0026amp; Pinion focuser provides zero-flexure support for full-frame imaging systems.\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\u003e132mm f\/6.9 FPL-53 Triplet: Pure Color Correction\u003c\/h3\u003e\n\u003cp\u003eAt the core of the Fluorostar 132 is a three-element objective lens featuring FPL-53 glass, the gold standard for color error correction. This apochromatic design virtually eliminates chromatic aberration, ensuring there is no spurious purple or green fringing around bright stars like Vega or on the limb of Jupiter. With high-transmission STM coatings, the FLT132 delivers exceptionally high contrast, revealing subtle planetary details and rendering stars as sharp, color-pure points against a black-sky background.\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\u003e3.7\" Rack \u0026amp; Pinion Focuser: 360° of Imaging Precision\u003c\/h3\u003e\n\u003cp\u003eDesigned for the demands of modern astrophotography, the FLT132 is equipped with a heavy-duty 3.7\" rack and pinion focuser. This large-aperture focuser can carry heavy imaging trains—including large-format cameras, filter wheels, and off-axis guiders—without sagging or flexure. For perfect composition, the entire focuser assembly rotates a full 360 degrees, allowing you to frame targets like the North American Nebula (NGC 7000) exactly as you wish without ever loosening your camera.\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 Robust 132mm OTA with CNC-Machined Precision\u003c\/h3\u003e\n\u003cp\u003eThe optical tube is crafted from solid CNC-machined aluminum, providing a rigid and thermally stable platform essential for consistent focus through long imaging sessions. The powder-painted white tube is durable and presents a classic, clean aesthetic. Every Fluorostar 132 includes a high-quality soft carrying case, protecting your investment during transport to dark-sky sites and making this powerful 132mm refractor surprisingly manageable.\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\u003eFLT132 vs. Standard 130mm Refractors: The 3.7\" Focuser Advantage\u003c\/h3\u003e\n\u003cp\u003eWhile many refractors in the 130mm class deliver excellent optical views, the Fluorostar 132 sets itself apart with its imaging-centric design, most notably its focuser.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eTypical Refractors:\u003c\/strong\u003e Many competitors use 2.5\" or 3\" focusers, which are adequate for smaller sensors but can become a bottleneck for flexure and illumination with larger cameras.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFluorostar 132:\u003c\/strong\u003e The 3.7\" focuser provides a wider, unvignetted light path for full-frame and larger sensors, especially when paired with a compatible reducer or flattener. Its robust build quality means you can invest in a heavy imaging setup without needing to budget for an immediate focuser upgrade.\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\"\u003eHow will the Fluorostar 132 perform on planetary targets like Jupiter with its 910mm focal length?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003eWilliam Optics Fluorostar 132\u003c\/strong\u003e is an excellent planetary instrument. Its 910mm focal length provides ample image scale for planets, and the FPL-53 triplet optics deliver the high-contrast, color-free views needed to resolve fine details like Jupiter's Great Red Spot, cloud bands, and the Cassini Division in Saturn's rings.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the FLT132 suitable for imaging large deep-sky objects like the Andromeda Galaxy (M31) with a full-frame camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. At its native 910mm focal length, the FLT132 will frame the core of M31 beautifully. When paired with a compatible field flattener or reducer, it provides a flat, well-corrected field for full-frame sensors. The large 3.7\" focuser is specifically designed to prevent vignetting and support the weight of a full-frame imaging setup.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat makes the FPL-53 triplet objective in the Fluorostar 132 superior to a doublet?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA \u003cstrong\u003etriplet objective\u003c\/strong\u003e with \u003cstrong\u003eFPL-53 glass\u003c\/strong\u003e corrects for chromatic aberration (false color) across a much wider spectrum than a standard doublet. This results in significantly higher contrast, sharper stars with no color fringing, and more faithful color rendition in astrophotos, which is especially critical for imaging and observing bright objects.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the benefit of the 3.7\" focuser on the William Optics FLT132?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003e3.7\" Rack \u0026amp; Pinion focuser\u003c\/strong\u003e offers two main advantages for astrophotography:\n\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigh Payload Capacity:\u003c\/strong\u003e It can hold heavy cameras, filter wheels, and other accessories without flexing or slipping, ensuring consistent focus.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFull Illumination:\u003c\/strong\u003e The large diameter prevents vignetting (darkening of the corners) on large camera sensors, such as full-frame DSLRs or dedicated astronomy cameras.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat field flatteners are compatible with the FLT132?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe William Optics Fluorostar 132 is designed to be compatible with several of their high-quality field flatteners and reducers, including the \u003cstrong\u003eP-FLAT68III\u003c\/strong\u003e, \u003cstrong\u003eP-Flat7A\u003c\/strong\u003e, and \u003cstrong\u003eP-Flat8\u003c\/strong\u003e. Using one of these accessories is recommended for astrophotography to ensure pinpoint stars across the entire field of view.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDoes the Fluorostar 132 come with a case for transport?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, the William Optics FLT132 includes a high-quality soft carrying case. This padded case is designed to protect the telescope during storage and transport to your observing location.\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\u003eAperture\u003c\/td\u003e\n\u003ctd\u003e132mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal Length\u003c\/td\u003e\n\u003ctd\u003e910mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal Ratio\u003c\/td\u003e\n\u003ctd\u003ef\/6.9\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eObjective Design\u003c\/td\u003e\n\u003ctd\u003eAir-Spaced Apochromatic Triplet\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eObjective Glass\u003c\/td\u003e\n\u003ctd\u003eFPL-53\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoatings\u003c\/td\u003e\n\u003ctd\u003eSTM Coatings\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocuser\u003c\/td\u003e\n\u003ctd\u003e3.7\" Rack \u0026amp; Pinion\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocuser Rotation\u003c\/td\u003e\n\u003ctd\u003e360 degrees\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTube Construction\u003c\/td\u003e\n\u003ctd\u003eCNC-machined Aluminum\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompatible Flatteners\u003c\/td\u003e\n\u003ctd\u003eP-FLAT68III, P-Flat7A, P-Flat8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Colors\u003c\/td\u003e\n\u003ctd\u003eRed, Gold, Grey\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\"\u003eFluorostar 132 Optical Tube Assembly\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\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":"Red \/ 3.3\" R\u0026P","offer_id":44967227457821,"sku":"WO-A-F132RDIII-RP33R","price":6304.0,"currency_code":"CAD","in_stock":true},{"title":"Red \/ 3.5\" Feather Touch","offer_id":44967227556125,"sku":"WO-A-F132RDIII-FTR","price":8162.0,"currency_code":"CAD","in_stock":true},{"title":"Gold \/ 3.3\" R\u0026P","offer_id":44967227425053,"sku":"WO-A-F132GDIII-RP33R","price":6304.0,"currency_code":"CAD","in_stock":true},{"title":"Gold \/ 3.5\" Feather Touch","offer_id":44967227490589,"sku":"WO-A-F132GDIII-FTR","price":8162.0,"currency_code":"CAD","in_stock":true},{"title":"Grey \/ 3.3\" R\u0026P","offer_id":48966062702877,"sku":"WO-A-F132TGIV-RP37","price":6897.0,"currency_code":"CAD","in_stock":true},{"title":"Grey \/ 3.5\" Feather Touch","offer_id":48966062735645,"sku":"WO-A-F132TGIV-FT","price":8162.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/William-Optics-FLT132-1.jpg?v=1722277044"},{"product_id":"william-optics-fluorostar-156","title":"William Optics Fluorostar 156","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e156mm Aperture Triplet Apochromat\u003c\/li\u003e\n\u003cli\u003e1217mm Focal Length (f\/7.8)\u003c\/li\u003e\n\u003cli\u003eFPL-53 \u0026amp; Lanthanum Glass Elements\u003c\/li\u003e\n\u003cli\u003e3.7\" Rack \u0026amp; Pinion Focuser\u003c\/li\u003e\n\u003cli\u003eThermally Stable Steel Objective Cell\u003c\/li\u003e\n\u003cli\u003eIntegrated Bahtinov Mask in Dust Cover\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 Fluorostar 156 f\/7.8 Triplet APO Refractor\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Fluorostar 156 combines a large 156mm aperture with a 1217mm (f\/7.8) focal length in a precision-engineered, air-spaced triplet optical system. Featuring premium FPL-53 glass and a Lanthanum element, this apochromatic refractor suppresses false color to undetectable levels, supported by a massive 3.7\" Rack \u0026amp; Pinion focuser for precise, no-slip focusing with heavy imaging payloads.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eA 156mm f\/7.8 Triplet APO: Color-Free Views with FPL-53 Glass\u003c\/h3\u003e\n\u003cp\u003eAt the heart of the Fluorostar 156 lies an air-spaced triplet objective that sets the standard for color correction and contrast. By combining a key element of FPL-53 glass with another of Lanthanum, the optical design brings all wavelengths of visible light to a single, sharp focal point. This eliminates the distracting purple fringing seen on bright stars in lesser instruments, delivering crisp, high-contrast views of planetary details and pinpoint stars across the entire field for astrophotography.\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\u003eThermally Stable Steel Cell: Maintaining Collimation at 156mm\u003c\/h3\u003e\n\u003cp\u003eA large 156mm objective lens is susceptible to subtle shifts as ambient temperature drops, which can degrade image sharpness. William Optics addresses this with a robust steel objective cell that mitigates thermal expansion and contraction. This ensures the triplet lens elements remain in perfect alignment throughout a long imaging session, preserving the exquisite optical correction from dusk until dawn.\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 Mechanics: A 3.7\" Focuser and Integrated Bahtinov Mask\u003c\/h3\u003e\n\u003cp\u003eThe Fluorostar 156 is built from the ground up for serious astrophotography. The heavy-duty 3.7\" rack and pinion focuser provides a rigid, stable platform for large cameras and filter wheels, eliminating flexure and focus shift. For achieving perfect focus, the lens cap features an integrated Bahtinov mask—a critical tool for hitting sharp focus in seconds. The entire optical tube is secured by three CNC-machined rings and a standard Losmandy-style dovetail plate, creating a solid foundation for any capable equatorial mount.\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 kind of mount is required for the William Optics Fluorostar 156?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eDue to its aperture and focal length, the Fluorostar 156 is a substantial instrument. A robust equatorial mount with a payload capacity of at least 50-60 lbs (22-27 kg) or more is strongly recommended for stable imaging and visual use. Mounts in the Celestron CGX, Losmandy G11, or Software Bisque Paramount MYT class are appropriate.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the FPL-53 and Lanthanum glass in the Fluorostar 156 benefit astrophotography?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis combination of exotic glass types provides exceptional apochromatic performance. For astrophotography, this means:\n\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eNo Chromatic Aberration:\u003c\/strong\u003e Bright stars like Vega or Sirius will not have distracting blue or purple halos, resulting in cleaner, more natural-looking star fields.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigher Contrast:\u003c\/strong\u003e By focusing all colors to the same point, fine details in nebulae and galaxies are not smeared or washed out, leading to sharper and more detailed images.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImproved Spectrographic Use:\u003c\/strong\u003e The clean color correction makes this an excellent instrument for use with narrowband filters (H-alpha, OIII, SII), as stars will be tight and round across all filtered channels.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the advantage of the integrated Bahtinov mask on the Fluorostar 156?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Bahtinov mask, integrated directly into the dust cover, is a significant convenience for astrophotographers. It creates a distinctive diffraction pattern around a bright star that instantly shows you when you have achieved perfect focus. This eliminates the guesswork of trying to find the point of sharpest focus by eye, saving valuable imaging time and ensuring your data is critically sharp every time.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use the Fluorostar 156 for visual observation as well as imaging?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAbsolutely. While optimized for imaging, the Fluorostar 156 is a superb visual instrument. Its 156mm aperture provides brilliant, high-resolution views of the Moon, planets, and deep-sky objects. The apochromatic optics deliver a pure, high-contrast image that is free of false color, making it ideal for discerning subtle cloud bands on Jupiter or resolving tight double stars.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow will the Fluorostar 156 perform on faint details in the Orion Nebula (M42)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Fluorostar 156's combination of 156mm aperture and high-contrast optics makes it an exceptional tool for M42. Visually, you can expect to resolve the E and F stars in the Trapezium cluster under good seeing conditions. For imaging, the 1217mm focal length perfectly frames the nebula's core while the sharp optics will capture the faint, intricate structures of the surrounding nebulosity with stunning clarity.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the 1217mm focal length of the Fluorostar 156 suitable for imaging smaller galaxies like the Whirlpool Galaxy (M51)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, the 1217mm focal length is an excellent match for medium-to-small deep-sky objects like M51, the Hercules Cluster (M13), or the Ring Nebula (M57). It provides enough image scale to resolve spiral arms, dust lanes, and individual stars in globular clusters, especially when paired with a modern astronomy camera with small pixels.\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\u003eAperture\u003c\/td\u003e\n\u003ctd\u003e156mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal Length\u003c\/td\u003e\n\u003ctd\u003e1217mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal Ratio\u003c\/td\u003e\n\u003ctd\u003ef\/7.8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Design\u003c\/td\u003e\n\u003ctd\u003eAir-Spaced Triplet Apochromat\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGlass Composition\u003c\/td\u003e\n\u003ctd\u003eFPL-53 \u0026amp; Lanthanum Elements\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocuser\u003c\/td\u003e\n\u003ctd\u003e3.7\" Rack \u0026amp; Pinion\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eObjective Cell Construction\u003c\/td\u003e\n\u003ctd\u003eSteel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Accent Colors\u003c\/td\u003e\n\u003ctd\u003eRed, Gold, Space Grey\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\"\u003eFluorostar 156 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\"\u003e3.7\" Rack \u0026amp; Pinion Focuser\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 Mask Cover\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\"\u003eCNC Tube Rings\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 3\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\"\u003eLosmandy-style Dovetail 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\"\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\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":"Red","offer_id":44967228080413,"sku":"WO-A-F156RD-RP37","price":10653.0,"currency_code":"CAD","in_stock":true},{"title":"Gold","offer_id":44967228014877,"sku":"WO-A-F156GD-RP37","price":12417.0,"currency_code":"CAD","in_stock":true},{"title":"Grey","offer_id":44967228047645,"sku":"WO-A-F156TG-RP37","price":12417.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/William-Optics-FLT156-1.jpg?v=1722277379"},{"product_id":"william-optics-fluorostar-91","title":"William Optics Fluorostar 91","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e91mm Aperture Apochromatic Triplet\u003c\/li\u003e\n\u003cli\u003eFPL-53 Glass for Superior Color Correction\u003c\/li\u003e\n\u003cli\u003eStrehl Ratio Exceeding 0.95\u003c\/li\u003e\n\u003cli\u003e3.3\" Dual-Speed Rack \u0026amp; Pinion Focuser\u003c\/li\u003e\n\u003cli\u003e360° Field Rotator for Image Framing\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\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 Fluorostar 91 APO Triplet Refractor\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Fluorostar 91 refractor combines a 91mm FPL-53 triplet objective with apochromatic correction, delivering images that demonstrate a Strehl ratio exceeding 0.95. Its robust 3.3\" rack and pinion focuser supports heavy imaging trains without flexure, while the 4.2 kg base tube weight ensures portability for demanding use in the field.\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\u003e91mm FPL-53 Triplet Optics: Strehl Ratio \u0026gt; 0.95 for High-Contrast Imaging\u003c\/h3\u003e\n\u003cp\u003eAt the core of the Fluorostar 91 is an air-spaced triplet objective featuring premium FPL-53 glass. This design virtually eliminates chromatic aberration, producing tack-sharp stars with pure color rendition. With a guaranteed Strehl ratio of over 0.95, this optic delivers maximum contrast, making it ideal for resolving fine planetary detail and capturing faint nebulosity against a dark sky background.\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\u003e3.3\" Rack \u0026amp; Pinion Focuser with 360° Field Rotator\u003c\/h3\u003e\n\u003cp\u003eEngineered for astrophotography, the FLT91 is equipped with a heavy-duty 3.3\" rack and pinion focuser. The dual-speed mechanism allows for coarse and fine adjustments, critical for achieving perfect focus with a camera. The entire focuser assembly includes a 360° field rotator for precise image framing, and the optical train terminates in a 2\" Rotolock adapter that provides a secure, self-centering grip on diagonals and 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\u003eImaging-Focused Design: Integrated Bahtinov Mask \u0026amp; 4.2 kg Tube Weight\u003c\/h3\u003e\n\u003cp\u003eEvery feature of the Fluorostar 91 is designed with the imager in mind. The lens cap contains an integrated Bahtinov mask, simplifying the process of achieving critical focus. An integrated saddle handle provides a secure grip and a mounting point for guide scopes or other accessories. Weighing only 4.2 kg (5.6 kg fully equipped), the FLT91 is easily managed by mid-sized equatorial mounts, creating a powerful yet portable deep-sky imaging system that comes protected in its own soft carry case.\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 makes the William Optics Fluorostar 91 an \"apochromatic triplet\"?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Fluorostar 91 is an \u003cstrong\u003eapochromatic triplet\u003c\/strong\u003e because it uses a three-element objective lens, including one element made from high-performance \u003cstrong\u003eFPL-53 glass\u003c\/strong\u003e. This combination brings the red, green, and blue wavelengths of light to the same focal point, eliminating distracting color fringing (chromatic aberration) for sharp, high-contrast images.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the 360° rotator on the FLT91 help with astrophotography?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003e360° field rotator\u003c\/strong\u003e allows you to change the orientation of your camera without loosening any screws or affecting focus. This is essential for composing your shot, letting you frame celestial objects like the Veil Nebula or the Rho Ophiuchi cloud complex perfectly within your sensor's field of view.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhich field flatteners are compatible with the Fluorostar 91?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe William Optics FLT91 is designed to be compatible with several William Optics flatteners, allowing for precise back-focus adjustments and a corrected field for various sensor sizes. Recommended models include:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eFlat 6AIII\u003c\/li\u003e\n\u003cli\u003eFlat 68III\u003c\/li\u003e\n\u003cli\u003eUltra Flat 91\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 Fluorostar 91 perform on emission nebulae like the North American Nebula (NGC 7000)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe FLT91's FPL-53 optics provide excellent color correction, especially in the red end of the spectrum where hydrogen-alpha emissions from nebulae like NGC 7000 are dominant. This results in tight, well-defined stars without the blue or violet halos that can plague lesser refractors, allowing the faint details of the nebula to stand out.\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 FLT91 for high-magnification planetary viewing of Jupiter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAbsolutely. The high Strehl ratio (\u003cstrong\u003e\u0026gt; 0.95\u003c\/strong\u003e) of the Fluorostar 91 ensures maximum contrast and sharpness. When seeing conditions are good, you can push the magnification to view fine details like the cloud bands of Jupiter, the Cassini Division in Saturn's rings, and subtle surface features on Mars.\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 integrated Bahtinov mask in the FLT91's lens cap?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe integrated \u003cstrong\u003eBahtinov mask\u003c\/strong\u003e is a focusing aid that creates a distinct diffraction pattern around a bright star. When the central spike is perfectly centered between the other two, you have achieved critical focus. This built-in tool saves time and removes the guesswork from focusing, ensuring your astrophotos are as sharp as possible.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Design\u003c\/td\u003e\n\u003ctd\u003eApochromatic Triplet Refractor\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAperture\u003c\/td\u003e\n\u003ctd\u003e91mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eObjective Glass\u003c\/td\u003e\n\u003ctd\u003eFPL-53\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eStrehl Ratio\u003c\/td\u003e\n\u003ctd\u003e\u0026gt; 0.95\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocuser\u003c\/td\u003e\n\u003ctd\u003e3.3\" Dual-Speed Rack \u0026amp; Pinion\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eField Rotator\u003c\/td\u003e\n\u003ctd\u003e360°\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eConnection\u003c\/td\u003e\n\u003ctd\u003e2\" Rotolock Adapter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFeatures\u003c\/td\u003e\n\u003ctd\u003eIntegrated Saddle Handle, Built-in Bahtinov Mask\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight (Tube Only)\u003c\/td\u003e\n\u003ctd\u003e4.2 kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight (Fully Equipped)\u003c\/td\u003e\n\u003ctd\u003e5.6 kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAvailable Colors\u003c\/td\u003e\n\u003ctd\u003eGrey, Gold, 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\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":"Grey","offer_id":44967782088989,"sku":"WO-T-FLT-91SG-RP33","price":3033.0,"currency_code":"CAD","in_stock":true},{"title":"Gold","offer_id":44967782023453,"sku":"WO-T-FLT-91GD-RP33","price":2877.0,"currency_code":"CAD","in_stock":true},{"title":"Red","offer_id":44967782056221,"sku":"WO-T-FLT-91RD-RP33","price":2877.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Williamo-Optics-FLT91-1.jpg?v=1722276083"},{"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-fluorostar-120","title":"William Optics Fluorostar 120","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e120mm Aperture\u003c\/li\u003e\n\u003cli\u003eFPL-53 Triplet Apochromatic Optics\u003c\/li\u003e\n\u003cli\u003e3.3\" Rack \u0026amp; Pinion Focuser\u003c\/li\u003e\n\u003cli\u003eBuilt-in Camera Angle Rotator\u003c\/li\u003e\n\u003cli\u003eIntegrated Bahtinov Mask\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 Fluorostar 120 Triplet APO Refractor\u003c\/h2\u003e\n      \u003cp\u003eThe William Optics Fluorostar 120 refractor combines a 120mm apochromatic triplet objective made with FPL-53 glass and a robust 3.3\" rack and pinion focuser for high-contrast, color-free astrophotography. Its imaging train begins with a native M92 thread and includes adapters for a 2\" RotoLock and a 1.25\" visual back, ensuring broad compatibility with your cameras and accessories.\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\u003eA 120mm FPL-53 Triplet for Pure-Color Imaging\u003c\/h3\u003e\n      \u003cp\u003eAt the heart of the Fluorostar 120 lies an air-spaced triplet objective featuring premium FPL-53 glass. This apochromatic design provides outstanding correction of chromatic aberration, eliminating the false color halos around bright stars that can compromise contrast and detail in lesser refractors. The result is a pristine, high-contrast image with pinpoint stars on a dark background, essential for capturing the subtle colors of nebulae and galaxies.\u003c\/p\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\n  \u003cdiv class=\"DAV-bg-light\"\u003e\n    \u003cdiv class=\"DAV-section\"\u003e\n      \u003ch3\u003eThe 3.3\" Rack \u0026amp; Pinion Focuser and Rotator System\u003c\/h3\u003e\n      \u003cp\u003eBuilt to handle heavy imaging loads, the heavy-duty 3.3\" rack and pinion focuser provides a rigid, zero-flexure platform for large cameras, filter wheels, and off-axis guiders. A built-in rotator allows you to frame your target perfectly without loosening the camera. The robust build necessary to support a full imaging rig means this is not a lightweight instrument; you will need a substantial mount to carry it effectively.\u003c\/p\u003e\n      \u003cul\u003e\n        \u003cli\u003e\n\u003cstrong\u003eNative Connection:\u003c\/strong\u003e The focuser drawtube terminates in a secure M92 thread.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003e2-Inch Adapter:\u003c\/strong\u003e An included adapter steps the connection down to a William Optics 2\" RotoLock, a self-centering system for accessories.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003e1.25-Inch Adapter:\u003c\/strong\u003e For visual use or smaller guide cameras, a final adapter provides a standard 1.25\" visual back.\u003c\/li\u003e\n      \u003c\/ul\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\u003eIntegrated Design: From M92 Threads to a Losmandy Plate\u003c\/h3\u003e\n      \u003cp\u003eThe Fluorostar 120 is engineered with practical features that streamline your imaging sessions. An integrated, patented Bahtinov Mask, built into the lens cap, is significantly lighter than traditional metal masks and makes achieving critical focus simple. The CNC-machined saddle handle bar not only provides a secure grip but also accepts Vixen-style mounting for guidescopes like the William Optics Uniguide. The entire optical tube assembly is secured by a sturdy Losmandy-style dovetail plate for a solid connection to your equatorial mount.\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\"\u003eWhat makes the Fluorostar 120's FPL-53 triplet design ideal for astrophotography?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe \u003cstrong\u003eFPL-53 glass\u003c\/strong\u003e in the Fluorostar 120's triplet lens system provides excellent correction of chromatic aberration. This means stars appear as sharp, color-pure points of light without distracting purple or blue halos, resulting in higher contrast and more natural-looking astrophotos.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the integrated Bahtinov mask on the Fluorostar 120 simplify focusing?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe patented Bahtinov Mask is built directly into the lens cap of the Fluorostar 120. To use it, you simply uncap the telescope, aim at a bright star, and adjust focus until the central diffraction spike is perfectly centered between the other two. This provides a fast, precise, and repeatable method for achieving critical focus every time you set up.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhat kind of imaging train can the Fluorostar 120's 3.3\" focuser support?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe heavy-duty \u003cstrong\u003e3.3\" rack and pinion focuser\u003c\/strong\u003e is designed to handle significant weight without slipping or flexing. It can easily support a full astrophotography setup, including a cooled astronomy camera, a large filter wheel, and an off-axis guider, ensuring your entire imaging train remains stable throughout the night.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the Fluorostar 120 perform when imaging the hydrogen-alpha regions in the Cygnus Loop (Veil Nebula)?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe Fluorostar 120's apochromatic optics excel at imaging emission nebulae like the Veil Nebula. The high-contrast views and excellent color correction allow the fine, filamentary details of the hydrogen-alpha structures to be captured with exceptional clarity against a dark sky background, especially when paired with narrowband filters.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhat are the benefits of the Fluorostar 120's rotator when framing a large target like the Andromeda Galaxy (M31) with a full-frame camera?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe built-in camera angle rotator on the Fluorostar 120 lets you adjust the orientation of your camera without having to loosen any other components in the imaging train. This is crucial for large targets like M31, as it allows you to precisely align the galaxy's long axis with your camera sensor's diagonal for the most compelling composition.\u003c\/p\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion\"\u003e\n    \u003ch3 class=\"DAV-accordion-Q\"\u003eWhat mounting hardware is included with the William Optics Fluorostar 120?\u003c\/h3\u003e\n  \u003c\/div\u003e\n  \u003cdiv class=\"DAV-accordion-A\"\u003e\n    \u003cp\u003eThe William Optics Fluorostar 120 comes with essential mounting hardware for immediate setup. This includes a CNC-machined handle that doubles as a Vixen-style saddle for accessories, mounting rings, and a Losmandy-style dovetail plate for secure attachment to a compatible equatorial mount.\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\u003eAvailable Options\u003c\/td\u003e\n\u003ctd\u003eRed, Gold, Space Gray\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n  \u003cul class=\"DAV-grid\"\u003e\n    \u003cli class=\"DAV-grid-item\"\u003e\n      \u003cdiv\u003e\n        \u003cp class=\"DAV-item-title\"\u003eM92 Rotator 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\"\u003eM92 to 2\" RotoLock 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\"\u003e2\" to 1.25\" Visual Back Adapter\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":"Red","offer_id":44967917682973,"sku":"WO-A-F120RD-RP33","price":4965.0,"currency_code":"CAD","in_stock":true},{"title":"Gold","offer_id":44967917650205,"sku":"WO-A-F120GD-RP33","price":4965.0,"currency_code":"CAD","in_stock":true},{"title":"Space Gray","offer_id":44967917715741,"sku":"WO-A-F120TG-RP33","price":4965.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/William-Optics-FLT120-1.jpg?v=1722276874"},{"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\/en-us\/collections\/william-optics-fluorostar-flt-apo-refractors.oembed","provider":"David Astro","version":"1.0","type":"link"}