{"product_id":"william-optics-cat-91-wifd-t-c-91","title":"William Optics Cat 91 WIFD Refractor (T-C-91)","description":"\u003ch1\u003eWilliam Optics Cat 91 WIFD\u003c\/h1\u003e\n\u003cp\u003eStep up your astrophotography game with the William Optics RedCat 91, an advanced apochromatic refractor tailored for full-frame and medium-format cameras. This latest addition to the RedCat series combines portability with superior optical performance, making it a versatile tool for capturing breathtaking detail in deep-sky objects.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHighlights:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePetzval Design, No Backfocus Hassles:\u003c\/strong\u003e The 5-element Petzval design eliminates the need for backfocus adjustments, providing sharp, edge-to-edge images with pinpoint stars—ideal for wide-field and detailed astrophotography alike.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFull-Frame \u0026amp; Medium-Format Ready, No Extra Flattener Needed:\u003c\/strong\u003e With a large 50mm image circle, the RedCat 91 is perfect for both full-frame and medium-format cameras. Its advanced optics achieve flat-field images without requiring an additional flattener, giving astrophotographers the freedom to capture expansive views with unparalleled clarity.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFast f\/4.9 Focal Ratio:\u003c\/strong\u003e The RedCat 91's fast f\/4.9 focal ratio is designed for bright, vivid captures of galaxies, nebulae, and beyond, ensuring excellent light-gathering power and sharp detail even on faint celestial objects.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSeamless WIFD Focusing:\u003c\/strong\u003e Equipped with William Optics' WIFD focuser, the RedCat 91 provides precise, stable focusing without additional adjustments, enhancing the ease of use for both seasoned astrophotographers and beginners.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThe RedCat 91 blends the trusted RedCat heritage with William Optics’ innovative design, making it the ultimate choice for those ready to elevate their night-sky explorations.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/redcat-91-wifd-hero.webp?v=1731167156\" alt=\"\"\u003e\u003c\/p\u003e\n\u003ch2 class=\"h3\"\u003eThe cat with medium-format soul\u003c\/h2\u003e\n\u003cdiv\u003e\n\u003cp\u003eAn advanced apochromatic refractor tailored for full-frame and medium-format cameras. This latest addition to the RedCat series combines portability with superior optical performance, making it a versatile tool for capturing breathtaking detail in deep-sky objects.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003ch2 class=\"h2\"\u003eAdvanced Petzval\u003c\/h2\u003e\n\u003cp\u003eResearched and developed by WO, the innovative 5-element Petzval design redefines telescope optics. This advanced system achieves a flawless spot diagram across a medium-format image circle.\u003c\/p\u003e\n\u003ch2 class=\"h3\"\u003eExtra-low Dispersion (ED) glasses\u003c\/h2\u003e\n\u003cp\u003eContains 2 Super ED, 1 ED glasses and lanthanum lenses with advanced fully multi-coated, delivering sharp, vibrant images with true-to-life colors, significantly reducing chromatic aberration.\u003c\/p\u003e\n\u003ch2 class=\"h3\"\u003eNeeds NO Flattener\u003c\/h2\u003e\n\u003cp\u003eThe Petzval design inherently flattens the field, eliminating the need for an external field flattener.\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/series-Diagram_Cat-91_1.webp?v=1731167324\" alt=\"\"\u003e\u003c\/p\u003e\n\u003ch3\u003e \u003c\/h3\u003e\n\u003ch2 class=\"h4\"\u003eCompatible with Electronic Motorized Devices\u003c\/h2\u003e\n\u003cdiv\u003e\n\u003cp\u003eHassle Free Installation\u003cbr\u003e\u003cstrong\u003e( No Mounting Bracket Kit required )\u003c\/strong\u003e\u003c\/p\u003e\n\u003ch2 class=\"h4\"\u003eInternal Focuser\u003c\/h2\u003e\n\u003cp\u003eThe WIFD focusing Design relocates the focuser to the center of the telescope, addresses the issue of tube tilt caused by the weight of accessories and cameras\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003c\/div\u003e\n\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\n\u003cp\u003eLens Type : 5-Element Advanced Petzval\u003c\/p\u003e\n\u003cp\u003eLens Elements : Super ED Glass x2 ED Glass x1 Lanthanum Glass x1\u003c\/p\u003e\n\u003cp\u003eFocal Length : 448 mm\u003c\/p\u003e\n\u003cp\u003eDiameter : 91 mm\u003c\/p\u003e\n\u003cp\u003eFocal Ratio : f\/4.9\u003c\/p\u003e\n\u003cp\u003eImage circle : 55 mm\u003c\/p\u003e\n\u003cp\u003eFocuser : WIFD R\u0026amp;P Focuser Compatible with EAF\u003c\/p\u003e\n\u003cp\u003eFocus : travel 0-36mm (Ruler to 40mm)\u003c\/p\u003e\n\u003cp\u003eAdapter Included : Tilt Adjuster Rotator M63 → M54 Adapter M63 → M48 Adapter\u003c\/p\u003e\n\u003cp\u003eOptional Flattener : No Flattener Required\u003c\/p\u003e\n\u003cp\u003eT-Mount Supported : Canon EF, RF Nikon F, Z Sony E Pentax K MFT (M4\/3) FUJI X\u003c\/p\u003e\n\u003cp\u003eCamera Format : Medium Format ( needs additional adapter ) Full Frame APS-C M4\/3\u003c\/p\u003e\n\u003cp\u003eTube Length : 556 mm\u003c\/p\u003e\n\u003cp\u003eOTA Weight : 4.72 kg \/ 10.41 lbs\u003c\/p\u003e\n\u003cp\u003eTotal Weight : 6.3 kg \/ 13.89 lbs\u003c\/p\u003e\n\u003ch3\u003eIn the Box\u003c\/h3\u003e\n\u003cp\u003e-William Optics Cat 91 WIFD\u003c\/p\u003e\n\u003cp\u003e-Bahtinov Cap\u003c\/p\u003e\n\u003cp\u003e-M48 \u0026amp; M54 Adapter\u003c\/p\u003e\n\u003cp\u003e-Mounting Plate\u003c\/p\u003e\n\u003cp\u003e-Mounting Ring Handle Bar\u003c\/p\u003e\n\u003cp\u003e-Soft Carry Case\u003c\/p\u003e\n\u003cp\u003e-Allen Key Set\u003c\/p\u003e\n\u003ch3\u003eWarranty \u0026amp; Manual\u003c\/h3\u003e\n\u003cp\u003e\u003ca title=\"William Optics 2-year Warranty\" href=\"https:\/\/istronomyplus.com\/pages\/william-optics-warranty?srsltid=AfmBOopOJhrnJJHCbIcAy4PqqyY3Z3eren5LqIaJQwywHgnuL-nCjtsn\" rel=\"noopener\" target=\"_blank\"\u003eWilliam Optics 2-year Warranty\u003c\/a\u003e\u003c\/p\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":46316749979877,"sku":"WO-T-C-91","price":4137.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/Cat-91-WIFD-pers-1.webp?v=1731167524","url":"https:\/\/istronomyplus.com\/products\/william-optics-cat-91-wifd-t-c-91","provider":"Astronomy Plus – Telescopes \u0026 Astrophotography Canada","version":"1.0","type":"link"}