{"product_id":"william-optics-cat-91-wifd-30th-anniversary-limited-edition","title":"William Optics Cat 91 WIFD · 30th Anniversary Limited Edition","description":"\u003cp\u003eThe \u003cstrong\u003eCat 91 WIFD · 30th Anniversary Edition\u003c\/strong\u003e is a commemorative refractor celebrating three decades of William Optics craftsmanship and innovation. Built upon the acclaimed five-element advanced Petzval optical design, this limited edition of \u003cstrong\u003e30 units worldwide\u003c\/strong\u003e combines uncompromising astrophotography performance with a symbolic anniversary finish.\u003c\/p\u003e\n\u003cp\u003eFeaturing a unique \u003cstrong\u003elaser-engraved emblem of a cat embracing “30”\u003c\/strong\u003e and accompanied by a \u003cstrong\u003e30th Anniversary Certificate\u003c\/strong\u003e, the Cat 91 WIFD is not only a professional imaging instrument but also a collector’s piece that honors the Cat series legacy.\u003c\/p\u003e\n\u003ch3\u003e\u003cspan\u003eHighlights:\u003cbr\u003e\u003c\/span\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003ePetzval Design, No Backfocus Hassles\u003cbr\u003e\u003c\/strong\u003eThe 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.\u003cbr\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eFull-Frame \u0026amp; Medium-Format Ready, No Extra Flattener Needed\u003cbr\u003e\u003c\/strong\u003eWith a large 55mm image circle, the Cat 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.\u003cbr\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eFast f\/4.9 Focal Ratio\u003cbr\u003e\u003c\/strong\u003eThe Cat 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.\u003cbr\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eSeamless WIFD Focusing\u003cbr\u003e\u003c\/strong\u003eEquipped with William Optics' WIFD focuser, the Cat 91 provides precise, stable focusing without additional adjustments, enhancing the ease of use for both seasoned astrophotographers and beginners.\u003c\/p\u003e\n\u003cdiv class=\"static-tabs__nav\"\u003e\u003cstrong\u003e\u003clabel class=\"static-tabs__tab-label h5\" for=\"tab-trigger-static_tab_item_6iKGhz\"\u003eSpecification; \u003c\/label\u003e\u003c\/strong\u003e\u003c\/div\u003e\n\u003cdiv class=\"static-tabs__content-wrapper\"\u003e\n\u003cdiv id=\"content-static_tab_item_6iKGhz\" class=\"static-tabs__content prose\"\u003e\n\u003cdiv class=\"definition specification\"\u003e\n\u003cdl\u003e\n\u003cdt\u003e\u003cstrong\u003eLens Type\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e5-Element Advanced Petzval\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eLens Elements\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e\n\u003cspan\u003eSuper ED Glass x2\u003c\/span\u003e \u003cspan\u003eED Glass x1\u003c\/span\u003e \u003cspan\u003eLanthanum Glass x1\u003c\/span\u003e \u003cspan\u003eX-Element x1\u003c\/span\u003e\n\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eFocal Length\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e448 mm\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eDiameter\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e91 mm\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eFocal Ratio\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003ef\/4.9\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eImage Circle\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e55 mm\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eFocuser\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e\n\u003cspan\u003eWIFD R\u0026amp;P Focuser\u003c\/span\u003e \u003cspan\u003eCompatible with EAF\u003c\/span\u003e\n\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eFocuser Travel\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e0-36 mm (Ruler to 40mm)\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eBack Spacing\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003eMaximum: M48 (60.8mm),M54 (65.8mm)\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eAdapter Included\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e\n\u003cspan\u003eTilt Adjuster\u003c\/span\u003e \u003cspan\u003eRotator\u003c\/span\u003e \u003cspan\u003eM63 → M54 Adapter\u003c\/span\u003e \u003cspan\u003eM63 → M48 Adapter\u003c\/span\u003e\n\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eOptional Flattener\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003eNo Flattener Required\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eT-Mount Support\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e\n\u003cspan\u003eCanon EF, RF\u003c\/span\u003e \u003cspan\u003eNikon F, Z\u003c\/span\u003e \u003cspan\u003eSony E\u003c\/span\u003e \u003cspan\u003ePentax K\u003c\/span\u003e \u003cspan\u003eMFT (M4\/3)\u003c\/span\u003e \u003cspan\u003eFUJI X\u003c\/span\u003e\n\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eCamera Format\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e\n\u003cspan\u003eMedium Format (needs additional adapter)\u003c\/span\u003e \u003cspan\u003eMedium Format\u003c\/span\u003e \u003cspan\u003eAPS-C\u003c\/span\u003e \u003cspan\u003eM4\/3\u003c\/span\u003e\n\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eDovetail Type\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003eVixen\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eTube Length\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e556 mm\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eOTA Weight\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e4.72 kg \/ 10.41 lbs\u003c\/dd\u003e\n\u003cdt\u003e\u003cstrong\u003eTotal Weight\u003c\/strong\u003e\u003c\/dt\u003e\n\u003cdd\u003e6.3 kg \/ 13.89 lbs\u003c\/dd\u003e\n\u003c\/dl\u003e\n\u003cp\u003e\u003cstrong\u003e\u003clabel class=\"static-tabs__tab-label h5\" for=\"tab-trigger-static_tab_item_PKd6ga\"\u003eDiagram Reports;\u003c\/label\u003e\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003ca href=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_Cat-91_1.jpg?v=1728521717\" target=\"_blank\"\u003e\u003cimg class=\"filter-invert-bw\" width=\"100%\" height=\"auto\" src=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_Cat-91_1.jpg?v=1728521717\"\u003e\u003c\/a\u003e\u003ca href=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_Cat-91_1-1.jpg?v=1730343493\" target=\"_blank\"\u003e \u003cimg class=\"filter-invert-bw\" width=\"100%\" height=\"auto\" src=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_Cat-91_1-1.jpg?v=1730343493\"\u003e\u003c\/a\u003e\u003ca href=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_Cat-91_2.jpg?v=1728521718\" target=\"_blank\"\u003e \u003cimg class=\"filter-invert-bw\" width=\"100%\" height=\"auto\" src=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_Cat-91_2.jpg?v=1728521718\"\u003e\u003c\/a\u003e\u003ca href=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_Cat-91_3.jpg?v=1728521717\" target=\"_blank\"\u003e \u003cimg class=\"filter-invert-bw\" width=\"100%\" height=\"auto\" src=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_Cat-91_3.jpg?v=1728521717\"\u003e\u003c\/a\u003e\u003ca href=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_Cat-91_4.jpg?v=1728521717\" target=\"_blank\"\u003e \u003cimg class=\"filter-invert-bw\" width=\"100%\" height=\"auto\" src=\"https:\/\/williamoptics.com\/cdn\/shop\/files\/Diagram_Cat-91_4.jpg?v=1728521717\"\u003e\u003c\/a\u003e\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e","brand":"William Optics","offers":[{"title":"Default Title","offer_id":54128896016698,"sku":null,"price":269800.0,"currency_code":"INR","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0691\/1456\/0826\/files\/a1_d4629b1b-8809-4715-a9c5-f1907edc91be.jpg?v=1790309135","url":"https:\/\/edisla.in\/products\/william-optics-cat-91-wifd-30th-anniversary-limited-edition","provider":"EDISLA","version":"1.0","type":"link"}