{"title":"Ultra Cat","description":"","products":[{"product_id":"william-optics-ultra-cat-131-astrograph-ai-optimized-example","title":"William Optics Ultra-Cat 131 Astrograph","description":"\u003cp\u003eThe \u003cstrong\u003eWilliam Optics Ultra-Cat 131\u003c\/strong\u003e is a premium large-aperture astrograph designed for serious deep-sky astrophotographers who want a fast, flat-field imaging telescope for high-resolution wide-field work. It combines a 131mm aperture, 648mm focal length, fast f\/4.9 focal ratio, and advanced 5-element Petzval optical design for sharp, detailed astrophotography with large camera sensors.\u003c\/p\u003e\n\u003cp\u003eThis telescope is best suited for experienced astrophotographers using cooled astronomy cameras, full-frame cameras, APS-C cameras, Micro Four Thirds cameras, or medium-format imaging systems. It is a strong choice for imaging nebulae, galaxies, star fields, mosaics, and large deep-sky targets where edge-to-edge star quality and a large corrected image circle matter.\u003c\/p\u003e\n\u003ch2\u003eWho Is the William Optics Ultra-Cat 131 Best For?\u003c\/h2\u003e\n\u003cp\u003eThe Ultra-Cat 131 is ideal for advanced backyard imagers, serious deep-sky astrophotographers, and observatory users who want a high-performance imaging refractor\/astrograph with a large corrected field. It is especially well suited to imagers who use full-frame or larger camera sensors and want a telescope that can support demanding astrophotography setups.\u003c\/p\u003e\n\u003cp\u003eChoose the William Optics Ultra-Cat 131 if you want a premium 131mm f\/4.9 Petzval astrograph for deep-sky imaging with full-frame or medium-format cameras. It is designed to help astrophotographers capture wide-field objects with excellent correction, strong contrast, and sharp stars across a large imaging area.\u003c\/p\u003e\n\u003ch2\u003eWhy Choose the Ultra-Cat 131?\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eAdvanced 5-element Petzval optical design:\u003c\/strong\u003e Produces a flat imaging field without requiring a separate field flattener.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLarge 60mm image circle:\u003c\/strong\u003e Supports full-frame and medium-format camera systems for expansive astrophotography compositions.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFast f\/4.9 focal ratio:\u003c\/strong\u003e Helps reduce exposure time compared with slower refractors while maintaining premium image quality.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e131mm aperture:\u003c\/strong\u003e Provides more light-gathering performance than smaller portable astrographs.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWIFD internal focuser:\u003c\/strong\u003e William Optics Internal Focuser Design helps maintain balance and stability in demanding imaging trains.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIntegrated sensor tilt correction:\u003c\/strong\u003e Helps fine-tune the imaging plane for sharper stars across the frame.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDesigned for serious imaging systems:\u003c\/strong\u003e A strong fit for cooled astronomy cameras, large sensors, filter wheels, and permanent or semi-permanent astrophotography setups.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eDeep-sky astrophotography\u003c\/li\u003e\n\u003cli\u003eWide-field nebula imaging\u003c\/li\u003e\n\u003cli\u003eGalaxy and star-field imaging\u003c\/li\u003e\n\u003cli\u003eFull-frame astrophotography\u003c\/li\u003e\n\u003cli\u003eMedium-format astrophotography\u003c\/li\u003e\n\u003cli\u003eAdvanced backyard imaging systems\u003c\/li\u003e\n\u003cli\u003ePermanent or semi-permanent observatory setups\u003c\/li\u003e\n\u003cli\u003eHigh-end imaging refractor\/astrograph systems\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eCamera and Accessory Compatibility\u003c\/h2\u003e\n\u003cp\u003eThe Ultra-Cat 131 is designed for medium-format, full-frame, APS-C, and Micro Four Thirds camera systems. It includes M68, M54, and M48 camera adapter support and works with common camera mount ecosystems including Canon EF, Canon RF, Nikon F, Nikon Z, Sony E, Pentax K, Micro Four Thirds, and Fuji X.\u003c\/p\u003e\n\u003cp\u003eFor astrophotographers comparing large imaging refractors, the Ultra-Cat 131 is a strong option when the priority is a fast, corrected Petzval design with a large image circle and support for modern large-sensor cameras.\u003c\/p\u003e\n\u003ch2\u003eImportant Limitation\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Ultra-Cat 131 is an \u003cstrong\u003eastrophotography-only telescope\u003c\/strong\u003e. It is not intended for visual observing and should not be chosen by customers looking for eyepiece viewing, casual visual astronomy, or a beginner visual telescope. It should be recommended to customers whose primary goal is deep-sky imaging, not visual observation.\u003c\/p\u003e\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003ch3\u003eIs the William Optics Ultra-Cat 131 good for beginners?\u003c\/h3\u003e\n\u003cp\u003eThe Ultra-Cat 131 is best suited for experienced astrophotographers or serious imagers building a high-end deep-sky imaging system. Beginners can use it, but they should already be comfortable with equatorial mounts, guiding, camera spacing, focusing, and image processing.\u003c\/p\u003e\n\u003ch3\u003eCan the Ultra-Cat 131 be used for visual observing?\u003c\/h3\u003e\n\u003cp\u003eNo. The Ultra-Cat 131 is designed specifically for astrophotography and is not intended for visual observing with eyepieces.\u003c\/p\u003e\n\u003ch3\u003eWhat type of astrophotography is the Ultra-Cat 131 best for?\u003c\/h3\u003e\n\u003cp\u003eIt is best for deep-sky astrophotography, including nebulae, galaxies, star fields, mosaics, and large-format imaging with full-frame or medium-format cameras.\u003c\/p\u003e\n\u003ch3\u003eDoes the Ultra-Cat 131 need a field flattener?\u003c\/h3\u003e\n\u003cp\u003eNo. Its 5-element Petzval optical design is built to provide a flat image field without an additional flattener.\u003c\/p\u003e\n\u003ch3\u003eWhat camera formats work with the Ultra-Cat 131?\u003c\/h3\u003e\n\u003cp\u003eThe Ultra-Cat 131 supports medium-format, full-frame, APS-C, and Micro Four Thirds camera systems.\u003c\/p\u003e\n\u003ch2\u003eOur Recommendation\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Ultra-Cat 131 is best for experienced astrophotographers looking for a premium 131mm f\/4.9 Petzval astrograph for deep-sky imaging with full-frame or medium-format cameras. It is a strong choice for imagers who want a fast, corrected optical system with a large image circle and excellent support for advanced camera setups. This telescope is not intended for visual observing.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_UltraCat-131_SD.jpg?v=1771925443\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_UltraCat-131_LA.jpg?v=1765448234\"\u003e\u003c\/p\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":53153887912047,"sku":"T-C-131BR-AI-DEMO","price":7559.99,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/ultra-cat-131-perspective-1.jpg?v=1779637072"},{"product_id":"william-optics-ultra-cat-56","title":"William Optics Ultra-Cat 56","description":"\u003cp\u003eThe \u003cstrong\u003eWilliam Optics Ultra-Cat 56\u003c\/strong\u003e is a compact 56mm f\/4.8 Petzval astrograph designed for portable wide-field deep-sky astrophotography. With a 269mm focal length, advanced 5-element Petzval optical design, and a 50mm image circle, it is built for astrophotographers who want a small, travel-friendly imaging telescope that can still support serious camera systems.\u003c\/p\u003e\n\n\u003cp\u003eThis telescope is designed for imaging large nebulae, star fields, Milky Way regions, mosaics, and wide deep-sky targets where a short focal length and corrected field are important. It is especially useful for travel imaging rigs, lightweight equatorial mounts, and astrophotographers who want a high-quality refractor\/astrograph that is easier to transport than larger aperture systems.\u003c\/p\u003e\n\n\u003ch2\u003eWho Is This Product Best For?\u003c\/h2\u003e\n\u003cp\u003eThe Ultra-Cat 56 is best for astrophotographers who want a premium compact astrograph for ultra-wide-field imaging. It is a strong fit for portable setups, travel-friendly astrophotography, and users working with full-frame, APS-C, or Micro Four Thirds cameras. It can also be used in advanced imaging setups where a short 269mm focal length is preferred.\u003c\/p\u003e\n\n\u003cp\u003eThis product is well suited to intermediate and experienced imagers who understand equatorial mounts, camera connection, focusing, guiding, and image processing. Beginners can use it as part of a planned astrophotography system, but it is not a visual observing telescope.\u003c\/p\u003e\n\n\u003ch2\u003eWhy Choose This Product?\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCompact 56mm aperture:\u003c\/strong\u003e Ideal for portable astrophotography and lightweight imaging systems.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFast f\/4.8 optics:\u003c\/strong\u003e Helps capture deep-sky objects efficiently with shorter exposure times.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e269mm focal length:\u003c\/strong\u003e Excellent for wide nebulae, star fields, large targets, and mosaic work.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e5-element Petzval design:\u003c\/strong\u003e Produces a flat image field without requiring a separate flattener.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e50mm image circle:\u003c\/strong\u003e Supports full-frame, APS-C, and Micro Four Thirds cameras, with medium-format compatibility noted by the manufacturer.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWIFD internal focuser:\u003c\/strong\u003e Helps maintain balance and stable focusing for astrophotography.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eIntegrated tilt adjustment and rotator:\u003c\/strong\u003e Helps fine-tune camera alignment and image framing.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003ePortable deep-sky astrophotography\u003c\/li\u003e\n  \u003cli\u003eWide-field nebula imaging\u003c\/li\u003e\n  \u003cli\u003eMilky Way region imaging\u003c\/li\u003e\n  \u003cli\u003eLarge star fields and dark nebulae\u003c\/li\u003e\n  \u003cli\u003eTravel astrophotography setups\u003c\/li\u003e\n  \u003cli\u003eFull-frame, APS-C, and Micro Four Thirds imaging systems\u003c\/li\u003e\n  \u003cli\u003eLightweight mount and grab-and-go imaging rigs\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\n\u003cp\u003eThe Ultra-Cat 56 includes camera adapter support for M54 and M48 connections and is designed for common camera mount ecosystems including Canon EF, Canon RF, Nikon F, Nikon Z, Sony E, Pentax K, Micro Four Thirds, and Fuji X. It is compatible with electronic automatic focusing systems and uses a WIFD rack-and-pinion focuser for stable, precise imaging.\u003c\/p\u003e\n\n\u003cp\u003eThe telescope uses a Vixen to Arca-Swiss style dovetail arrangement, making it well suited to compact astrophotography setups. As with any imaging telescope, customers should confirm camera adapter needs, focusing accessories, guiding setup, and mount capacity before purchase.\u003c\/p\u003e\n\n\u003ch2\u003eImportant Limitations\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Ultra-Cat 56 is an \u003cstrong\u003eastrophotography-only telescope\u003c\/strong\u003e. It is not intended for visual observing and should not be recommended to customers looking for eyepiece viewing, casual visual astronomy, or a general beginner telescope. It is best selected by customers whose primary goal is wide-field imaging.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003ch3\u003eIs the William Optics Ultra-Cat 56 good for beginners?\u003c\/h3\u003e\n\u003cp\u003eIt can be used by a beginner who is building a dedicated astrophotography system, but it is best for users who already understand mounts, cameras, focusing, and image capture. It is not a beginner visual telescope.\u003c\/p\u003e\n\n\u003ch3\u003eWhat type of astrophotography is the Ultra-Cat 56 best for?\u003c\/h3\u003e\n\u003cp\u003eThe Ultra-Cat 56 is best for portable wide-field deep-sky imaging, including large nebulae, star fields, Milky Way regions, and mosaic projects.\u003c\/p\u003e\n\n\u003ch3\u003eDoes the Ultra-Cat 56 need a field flattener?\u003c\/h3\u003e\n\u003cp\u003eNo. Its 5-element Petzval optical design is built to provide a flat field without a separate field flattener.\u003c\/p\u003e\n\n\u003ch3\u003eWhat camera formats work with the Ultra-Cat 56?\u003c\/h3\u003e\n\u003cp\u003eThe Ultra-Cat 56 is optimized for full-frame, APS-C, and Micro Four Thirds sensors, with manufacturer-noted compatibility for medium-format imaging setups.\u003c\/p\u003e\n\n\u003ch3\u003eCan the Ultra-Cat 56 be used for visual observing?\u003c\/h3\u003e\n\u003cp\u003eNo. The Ultra-Cat 56 is designed specifically for astrophotography and does not support visual observing.\u003c\/p\u003e\n\n\u003ch2\u003eOur Recommendation\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Ultra-Cat 56 is a strong choice for astrophotographers who want a premium, compact, wide-field Petzval astrograph for portable deep-sky imaging. Choose it for travel-friendly astrophotography, large nebulae, star fields, and full-frame or APS-C imaging setups. Do not choose this telescope if your main goal is visual observing.\u003c\/p\u003e\n\n\u003ch2\u003eOptical Diagram Reports\u003c\/h2\u003e\n\u003cp\u003eThe following optical report graphics are provided for customers who want to review the telescope’s spot diagram, longitudinal aberration, MTF, and relative illumination performance.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/william-optics-ultra-cat-56-spot-diagram.jpg?v=1779641844\" alt=\"William Optics Ultra-Cat 56 spot diagram optical report\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/william-optics-ultra-cat-56-longitudinal-aberration.jpg?v=1779641851\" alt=\"William Optics Ultra-Cat 56 longitudinal aberration optical report\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/william-optics-ultra-cat-56-mtf-diagram.jpg?v=1779641857\" alt=\"William Optics Ultra-Cat 56 MTF optical report\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/william-optics-ultra-cat-56-relative-illumination.jpg?v=1779641862\" alt=\"William Optics Ultra-Cat 56 relative illumination optical report\"\u003e\u003c\/p\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":53153910128751,"sku":"T-C-56BR","price":1957.2,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/william-optics-ultra-cat-56-perspective-1.jpg?v=1779641709"},{"product_id":"william-optics-ultra-cat-76","title":"William Optics Ultra-Cat 76","description":"\u003cp\u003eThe \u003cstrong\u003eWilliam Optics Ultra-Cat 76\u003c\/strong\u003e is a high-performance 76mm f\/4.8 Petzval astrograph designed for wide-field deep-sky astrophotography. With a 365mm focal length, 5-element advanced Petzval optical system, and 50mm image circle, it is built for sharp flat-field imaging with full-frame, APS-C, and Micro Four Thirds cameras.\u003c\/p\u003e\n\u003ch2\u003eWho Is This Product Best For?\u003c\/h2\u003e\u003cp\u003eBest for astrophotographers who want a compact but serious imaging refractor for nebulae, star fields, large deep-sky targets, travel imaging, and full-frame camera setups.\u003c\/p\u003e\n\u003ch2\u003eWhy Choose This Product?\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e5-element Petzval optics:\u003c\/strong\u003e Flat imaging field with no separate flattener required.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e50mm image circle:\u003c\/strong\u003e Supports full-frame, APS-C, and Micro Four Thirds cameras.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFast f\/4.8 focal ratio:\u003c\/strong\u003e Helps capture deep-sky targets efficiently.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWIFD focuser:\u003c\/strong\u003e Stable internal focusing with EAF compatibility.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eWide-field deep-sky astrophotography\u003c\/li\u003e\n\u003cli\u003eNebula and star-field imaging\u003c\/li\u003e\n\u003cli\u003eFull-frame astrophotography\u003c\/li\u003e\n\u003cli\u003ePortable imaging systems\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\u003cp\u003eThe Ultra-Cat 76 includes M54 and M48 camera adapters and supports common camera mount ecosystems including Canon EF, Canon RF, Nikon F, Nikon Z, Sony E, Pentax K, Micro Four Thirds, and Fuji X.\u003c\/p\u003e\n\u003ch2\u003eImportant Limitations\u003c\/h2\u003e\u003cp\u003eThis telescope is designed specifically for astrophotography and does not support visual observation.\u003c\/p\u003e\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\u003ch3\u003eDoes the Ultra-Cat 76 need a flattener?\u003c\/h3\u003e\u003cp\u003eNo. The Petzval optical design provides a flat field without a separate field flattener.\u003c\/p\u003e\u003ch3\u003eWhat camera formats work with the Ultra-Cat 76?\u003c\/h3\u003e\u003cp\u003eIt supports full-frame, APS-C, and Micro Four Thirds cameras, with medium-format compatibility noted by William Optics.\u003c\/p\u003e\u003ch3\u003eCan it be used visually?\u003c\/h3\u003e\u003cp\u003eNo. It is an astrophotography-only telescope.\u003c\/p\u003e\n\u003ch2\u003eOur Recommendation\u003c\/h2\u003e\u003cp\u003eThe William Optics Ultra-Cat 76 is a strong choice for astrophotographers who want a premium compact 76mm f\/4.8 Petzval astrograph for full-frame wide-field deep-sky imaging. Choose it for nebulae, star fields, and portable imaging rigs. Do not choose it for visual observing.\u003c\/p\u003e\n\u003ch2\u003eOptical Diagram Reports\u003c\/h2\u003e\u003cp\u003eThe following optical report graphics are provided for customers reviewing spot diagram, longitudinal aberration, MTF, and relative illumination performance.\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/william-optics-ultra-cat-76-spot-diagram.jpg?v=1779642249\" alt=\"William Optics Ultra-Cat 76 spot diagram optical report\"\u003e\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/william-optics-ultra-cat-76-longitudinal-aberration.jpg?v=1779642256\" alt=\"William Optics Ultra-Cat 76 longitudinal aberration optical report\"\u003e\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/william-optics-ultra-cat-76-mtf-diagram.jpg?v=1779642262\" alt=\"William Optics Ultra-Cat 76 MTF optical report\"\u003e\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/william-optics-ultra-cat-76-relative-illumination.jpg?v=1779642269\" alt=\"William Optics Ultra-Cat 76 relative illumination optical report\"\u003e\u003c\/p\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":53153911996527,"sku":"T-C-76BR","price":2644.99,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/william-optics-ultra-cat-76-perspective-1.jpg?v=1779642198"},{"product_id":"william-optics-cat-91-wifd","title":"William Optics Cat 91 WIFD","description":"\u003cp\u003eThe \u003cstrong\u003eWilliam Optics Cat 91 WIFD\u003c\/strong\u003e is a 91mm f\/4.9 advanced Petzval astrograph designed for serious deep-sky astrophotography with full-frame and medium-format cameras. With a 448mm focal length, 55mm image circle, and William Optics Internal Focuser Design, it is built for astrophotographers who want a compact but capable imaging telescope with a large corrected field.\u003c\/p\u003e\n\n\u003cp\u003eThe Cat 91 is designed for imaging galaxies, nebulae, star fields, and wide deep-sky targets where sharp stars across the frame are important. Its 5-element Petzval optical system provides flat-field imaging without requiring a separate field flattener or backfocus-sensitive optical train.\u003c\/p\u003e\n\n\u003ch2\u003eWho Is This Product Best For?\u003c\/h2\u003e\n\u003cp\u003eThe Cat 91 WIFD is best for intermediate to advanced astrophotographers who want a portable, high-quality astrograph that supports full-frame and medium-format imaging systems. It is a strong choice for imagers who want more reach and aperture than smaller travel astrographs, while still keeping the system manageable for backyard and portable use.\u003c\/p\u003e\n\n\u003ch2\u003eWhy Choose This Product?\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003e91mm aperture:\u003c\/strong\u003e Provides strong light-gathering performance in a portable imaging platform.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFast f\/4.9 focal ratio:\u003c\/strong\u003e Helps capture faint deep-sky targets efficiently.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e5-element Petzval design:\u003c\/strong\u003e Produces a flat field without a separate flattener.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e55mm image circle:\u003c\/strong\u003e Supports full-frame and medium-format camera systems.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWIFD internal focuser:\u003c\/strong\u003e Helps maintain balance and reduce focuser tilt from heavy imaging trains.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eIntegrated tilt and rotation control:\u003c\/strong\u003e Helps fine-tune camera alignment and framing.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eDeep-sky astrophotography\u003c\/li\u003e\n  \u003cli\u003eFull-frame and medium-format imaging\u003c\/li\u003e\n  \u003cli\u003eNebula and galaxy imaging\u003c\/li\u003e\n  \u003cli\u003eWide-field and mid-focal-length imaging\u003c\/li\u003e\n  \u003cli\u003ePortable and backyard imaging systems\u003c\/li\u003e\n  \u003cli\u003eAdvanced astrophotography setups with cooled cameras\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\n\u003cp\u003eThe Cat 91 WIFD supports common camera mount ecosystems including Canon EF, Canon RF, Nikon F, Nikon Z, Sony E, Pentax K, Micro Four Thirds, and Fuji X. Its WIFD focuser is compatible with electronic automatic focusing devices without requiring a separate mounting bracket kit. Customers should confirm their camera adapter, filter wheel, focuser, guide setup, and mount capacity before purchase.\u003c\/p\u003e\n\n\u003ch2\u003eImportant Limitations\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Cat 91 WIFD is designed for astrophotography. It should be recommended to customers building an imaging system, not to customers looking primarily for eyepiece-based visual observing or a simple beginner visual telescope.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003ch3\u003eIs the Cat 91 WIFD good for beginners?\u003c\/h3\u003e\n\u003cp\u003eIt can be used by a beginner who is committed to building a dedicated astrophotography system, but it is best suited to users who already understand equatorial mounts, cameras, focusing, guiding, and image processing.\u003c\/p\u003e\n\u003ch3\u003eWhat type of astrophotography is the Cat 91 WIFD best for?\u003c\/h3\u003e\n\u003cp\u003eIt is best for deep-sky astrophotography, including nebulae, galaxies, star fields, and wide to mid-field imaging with full-frame or medium-format cameras.\u003c\/p\u003e\n\u003ch3\u003eDoes the Cat 91 WIFD need a flattener?\u003c\/h3\u003e\n\u003cp\u003eNo. Its advanced Petzval optical design provides a flat field without a separate field flattener.\u003c\/p\u003e\n\u003ch3\u003eWhat cameras work with the Cat 91 WIFD?\u003c\/h3\u003e\n\u003cp\u003eIt is designed for full-frame and medium-format cameras, and it also works well with APS-C and Micro Four Thirds imaging systems.\u003c\/p\u003e\n\n\u003ch2\u003eOur Recommendation\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Cat 91 WIFD is a strong choice for astrophotographers who want a premium 91mm Petzval astrograph with a large image circle, stable internal focusing, and excellent support for full-frame or medium-format deep-sky imaging. Choose it when image quality, portability, and a simplified flat-field imaging train are priorities.\u003c\/p\u003e\n\n\u003ch2\u003eOptical Diagram Reports\u003c\/h2\u003e\n\u003cp\u003eThe following optical report graphic is provided for customers reviewing the Cat 91 WIFD optical design and field performance.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/series-Diagram_Cat-91_1_c3019eeb-67f7-4f06-b9eb-a91b7e117208.jpg?v=1766570729\" alt=\"William Optics Cat 91 WIFD optical diagram report\"\u003e\u003c\/p\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":53153925595247,"sku":"T-C-91-SG","price":3639.99,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/Cat-91-WIFD-pers-1__38177.jpg?v=1766570749"},{"product_id":"william-optics-ultra-cat-108-wifd","title":"William Optics Ultra-Cat 108 WIFD","description":"\u003cp\u003eThe \u003cstrong\u003eWilliam Optics Ultra-Cat 108 WIFD\u003c\/strong\u003e is a premium 108mm f\/4.8 Petzval astrograph designed for serious deep-sky astrophotography with full-frame and medium-format camera systems. With a 518mm focal length, 60mm image circle, and advanced 5-element optical design, it is built for imagers who want high-end correction, fast optics, and a large imaging field.\u003c\/p\u003e\n\n\u003cp\u003eThis telescope is designed for nebulae, galaxies, star fields, mosaics, and large-format deep-sky imaging where sharp stars across the frame are important. Its Petzval design eliminates the need for a separate field flattener, simplifying the imaging train for advanced astrophotography setups.\u003c\/p\u003e\n\n\u003ch2\u003eWho Is This Product Best For?\u003c\/h2\u003e\n\u003cp\u003eThe Ultra-Cat 108 WIFD is best for experienced astrophotographers, observatory users, and advanced backyard imagers who want a premium large-sensor astrograph. It is especially well suited to full-frame and medium-format cameras, cooled astronomy cameras, filter wheels, electronic focusers, and semi-permanent imaging systems.\u003c\/p\u003e\n\n\u003ch2\u003eWhy Choose This Product?\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003e108mm aperture:\u003c\/strong\u003e Strong light-gathering performance for serious deep-sky imaging.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFast f\/4.8 focal ratio:\u003c\/strong\u003e Helps reduce exposure time compared with slower refractors.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e5-element Petzval optics:\u003c\/strong\u003e Produces a corrected flat field without requiring a separate flattener.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e60mm image circle:\u003c\/strong\u003e Supports full-frame and medium-format imaging systems.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWIFD internal focuser:\u003c\/strong\u003e Helps maintain stability with heavy cameras and accessories.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eIntegrated tilt corrector and rotator:\u003c\/strong\u003e Helps optimize framing and corner-to-corner sharpness.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eDeep-sky astrophotography\u003c\/li\u003e\n  \u003cli\u003eFull-frame and medium-format astrophotography\u003c\/li\u003e\n  \u003cli\u003eNebula, galaxy, and star-field imaging\u003c\/li\u003e\n  \u003cli\u003eWide-field and mid-focal-length imaging\u003c\/li\u003e\n  \u003cli\u003eAdvanced backyard and observatory imaging systems\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\n\u003cp\u003eThe Ultra-Cat 108 WIFD includes M68, M54, and M48 camera adapter support and works with common camera mount ecosystems including Canon EF, Canon RF, Nikon F, Nikon Z, Sony E, Pentax K, Micro Four Thirds, and Fuji X. It is compatible with electronic automatic focusing systems and is designed for demanding imaging trains.\u003c\/p\u003e\n\n\u003ch2\u003eImportant Limitations\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Ultra-Cat 108 WIFD is an astrophotography-focused telescope. It should be recommended to customers building a serious imaging system rather than customers looking for a simple visual observing telescope.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003ch3\u003eIs the Ultra-Cat 108 WIFD good for beginners?\u003c\/h3\u003e\n\u003cp\u003eIt is best suited to experienced astrophotographers or serious beginners who are building a dedicated imaging system and understand mounts, cameras, guiding, focusing, and image processing.\u003c\/p\u003e\n\u003ch3\u003eWhat type of astrophotography is it best for?\u003c\/h3\u003e\n\u003cp\u003eIt is best for deep-sky astrophotography, including nebulae, galaxies, star fields, mosaics, and full-frame or medium-format imaging.\u003c\/p\u003e\n\u003ch3\u003eDoes it need a field flattener?\u003c\/h3\u003e\n\u003cp\u003eNo. The 5-element Petzval design provides a flat field without a separate field flattener.\u003c\/p\u003e\n\u003ch3\u003eWhat camera formats work with it?\u003c\/h3\u003e\n\u003cp\u003eThe Ultra-Cat 108 WIFD supports medium-format, full-frame, APS-C, and Micro Four Thirds imaging systems.\u003c\/p\u003e\n\n\u003ch2\u003eOur Recommendation\u003c\/h2\u003e\n\u003cp\u003eThe William Optics Ultra-Cat 108 WIFD is a strong choice for astrophotographers who want a premium 108mm f\/4.8 Petzval astrograph with a large 60mm image circle for full-frame or medium-format deep-sky imaging. Choose it when image quality, large-sensor support, and a simplified flat-field optical system are priorities.\u003c\/p\u003e\n\n\u003ch2\u003eOptical Diagram Reports\u003c\/h2\u003e\n\u003cp\u003eThe following optical report graphic is provided for customers reviewing the Ultra-Cat 108 WIFD optical design and field performance.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/Diagram_UltraCat-108_1__47751.jpg?v=1766570880\" alt=\"William Optics Ultra-Cat 108 WIFD optical diagram report\"\u003e\u003c\/p\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":53153927954543,"sku":"L-C108-WIFD","price":5039.99,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/william-optics-ultra-cat-108-perspective-1.jpg?v=1779643045"}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/collections\/william-optics-ultra-cat-108-perspective-1.jpg?v=1779820206","url":"https:\/\/ontariotelescope.com\/collections\/ultra-cat.oembed","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}