{"id":33717,"date":"2025-11-14T14:19:40","date_gmt":"2025-11-14T13:19:40","guid":{"rendered":"https:\/\/www.telescoop.nl\/?post_type=product&#038;p=33717"},"modified":"2026-10-13T11:15:23","modified_gmt":"2026-10-13T09:15:23","slug":"william-optics-blackcat-91-448-apo-wifd-ota","status":"publish","type":"product","link":"https:\/\/www.telescoop.nl\/en\/william-optics-blackcat-91-448-apo-wifd-ota\/","title":{"rendered":"William Optics BlackCat 91\/448 APO WIFD OTA"},"content":{"rendered":"<h2 class=\"wp-block-heading has-text-align-center\"><strong>BlackCat 91: the complete imaging execution<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The <strong>William Optics BlackCat 91 WIFD<\/strong> is the most complete version in the Cat 91 class. The 91 mm Petzval optics with FPL53 and FPL51 glass deliver a color-pure, sharp image all the way to the edges of a full-frame sensor, and the included rotator and tilt flange provide complete control over composition and sensor alignment.<\/p>\n\n\n\n<figure class=\"wp-block-gallery has-nested-images columns-default is-cropped wp-block-gallery-1 is-layout-flex wp-block-gallery-is-layout-flex\">\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" data-id=\"33718\" src=\"https:\/\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-AP-91-448-91-Apochromatische-refractor-BlackCat-WIFD-OTA-11.jpg\" alt=\"William Optics BlackCat 91 WIFD apochromatic astrograph, full view\" class=\"wp-image-33718\" title=\"\"><\/figure>\n<\/figure>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-8d39b2df wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-AP-91-448-91-Apochromatische-refractor-BlackCat-WIFD-OTA-7.jpg\" alt=\"The BlackCat 91 with rotator and tilt flange\" class=\"wp-image-33722\" title=\"\"><\/figure>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<h4 class=\"wp-block-heading\">Everything for the perfect recording<\/h4>\n\n\n\n<p class=\"wp-block-paragraph\">With f\/4.9 and a 448 mm focal length, you can photograph medium-sized nebulae and galaxies with short exposures. The rotator rotates the composition without touching the focus, the tilt flange corrects sensor tilt, and the M48 and M54 adapters connect virtually any camera train directly. The internal WIFD focuser supports all of that without sagging.<\/p>\n<\/div>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>In the box<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Optical tube Cat 91\/448 with WIFD focuser<\/li>\n\n\n\n<li>Rotator<\/li>\n\n\n\n<li>Candelabra<\/li>\n\n\n\n<li>M48 and M54 adapters<\/li>\n\n\n\n<li>Dovetail pliers<\/li>\n\n\n\n<li>Integrated Bahtinov mask<\/li>\n\n\n\n<li>Nylon tote bag<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Featured accessories<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A <a href=\"https:\/\/www.telescoop.nl\/en\/telescope-accessories\/astro-photography\/other-astrophotography-accessories\/\">William Optics UniGuide 50mm Guidescope<\/a> (from 189 euros) is the fitting guide for this class. The M48 and M54 connectors directly accept common William Optics camera adapters.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">For whom yes, for whom no<\/h4>\n\n\n\n<p class=\"wp-block-paragraph\">Pros: advanced astrophotographers who want maximum control over composition and sensor alignment, in the black version. Cons: those looking for the same optics without a rotator and tilt adapter; the RedCat 91 WIFD is the more simply equipped choice in that case.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Specifications<\/strong><\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td>Optical design<\/td><td>Apochromat, Petzval (FPL53 and FPL51)<\/td><\/tr><tr><td>Opening<\/td><td>91 millimeters<\/td><\/tr><tr><td>Focal length<\/td><td>448 mm<\/td><\/tr><tr><td>Opening ratio<\/td><td>f\/4,9<\/td><\/tr><tr><td>Focuser<\/td><td>WIFD (intern)<\/td><\/tr><tr><td>Rotator and tilt flange<\/td><td>Included<\/td><\/tr><tr><td>Camera connection<\/td><td>M48 and M54<\/td><\/tr><tr><td>Field of view<\/td><td>Flat to full-frame<\/td><\/tr><tr><td>Execution<\/td><td>OTA (loose tube)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Unsure about the right tube for your camera and mount? The <a href=\"https:\/\/www.telescoop.nl\/en\/telescope-selection-aid\/\">telescope selection aid<\/a> helps you choose. Also view all <a href=\"https:\/\/www.telescoop.nl\/en\/telescopes\/refracting-telescopes\/\">Refracting telescopes<\/a> and the full range of <a href=\"https:\/\/www.telescoop.nl\/en\/brands\/william-optics\/\">William Optics<\/a>.<\/p>","protected":false},"excerpt":{"rendered":"<p><strong>This is just the tube (OTA), without mounting and tripod.<\/strong> You can choose the appropriate mounting and the accessories that come with it below.<\/p>\n<p>William Optics BlackCat 91 WIFD: Petzval apochromat 91\/448 f\/4.9 with rotator, tilt flange, and M48\/M54 adapters. Color-pure, flat image up to full-frame. Supplied with dovetail bar, Bahtinov mask, and carrying case.<\/p>","protected":false},"featured_media":97249,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false},"product_brand":[643],"product_cat":[51,428,3175,567],"product_tag":[3352,3353],"class_list":["post-33717","product","type-product","status-publish","has-post-thumbnail","product_brand-william-optics","product_cat-telescopen","product_cat-telescopen-voor-astrofotografie","product_cat-refractor-ota","product_cat-refractor-telescopen","product_tag-sterrenkijker","product_tag-sterrenkijkers","first","instock","taxable","shipping-taxable","purchasable","product-type-simple"],"bundled_by":[],"bundle_stock_status":"instock","bundle_stock_quantity":null,"bundle_virtual":false,"bundle_layout":"","bundle_add_to_cart_form_location":"","bundle_editable_in_cart":false,"bundle_sold_individually_context":"","bundle_item_grouping":"","bundle_min_size":"","bundle_max_size":"","bundle_price":[],"bundled_items":[],"bundle_sell_ids":[90626,27732,32949,34220,15860,34033,33941,33946,34082],"acf":[],"jetpack_sharing_enabled":true,"jetpack-related-posts":[{"id":33729,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-redcat-91-448-apo-wifd-red-ota\/","url_meta":{"origin":33717,"position":0},"title":"William Optics RedCat 91\/448 APO WIFD Red OTA","author":"","date":"14-11-2025","format":false,"excerpt":"This is just the tube (OTA), without mounting and tripod. You can choose the appropriate mounting and the accessories that come with it below. William Optics RedCat 91 WIFD: Petzval achromatic lens 91\/448 f\/4.9 in red version, with M48\/M54 adapters and internal focusers. Supplied with dovetail rod, Bahtinov mask and carrying case.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-AP-91-448-91-Apochromatische-refractor-RedCat-WIFD-OTA-2.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":33639,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-ap-108-518-apochromatische-refractor-ultracat-wifd\/","url_meta":{"origin":33717,"position":1},"title":"William Optics AP 108\/518 Apochromatic Refractor UltraCat WIFD OTA","author":"","date":"14-11-2025","format":false,"excerpt":"This is just the tube (OTA), without the mount and tripod. You can choose the appropriate mount and the accessories that come with it below. William Optics UltraCat 108 WIFD: full-frame flagship 108\/518 f\/4.8 with integrated Petzval corrector, rotator, tilt lens and internal focuser. Supplied with Bahtinov mask and Vixen owl tail.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-Apochromatische-refractor-AP-108-518-UltraCat-WIFD.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":33664,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-ap-51-250-apochromatische-refractor-spacecat-wifd-ota\/","url_meta":{"origin":33717,"position":2},"title":"William Optics AP 51\/250 Apochromatic Refractor SpaceCat WIFD OTA","author":"","date":"14-11-2025","format":false,"excerpt":"This is just the tube (OTA), without mounting and tripod. You can choose the appropriate mounting and the accessories that come with it below. William Optics SpaceCat 51 WIFD: the same f\/4.9 Petzval optics as the RedCat 51 in the SpaceCat version, with internal focus. Supplied with a Bahtinov mask, prism bar and carrying case.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-AP-51250-Apochromatische-refractor-SpaceCat-WIFD-OTA-1.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":33659,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-ap-51-250-apochromatische-refractor-redcat-wifd\/","url_meta":{"origin":33717,"position":3},"title":"William Optics AP 51\/250 Apochromatic Refractor RedCat WIFD OTA","author":"","date":"14-11-2025","format":false,"excerpt":"This is just the tube (OTA), without mounting and tripod. A suitable mounting and the accessories that come with it can be selected below. William Optics RedCat 51 WIFD: the most famous compact astrograph with four-lens Petzval optics (FPL53\/FPL51) and internal focus. Flat, color-pure image up to full-frame. Supplied with Bahtinov mask, prism bar and carrying case.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-AP-51250-Apochromatische-refractor-RedCat-WIFD-4.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":33699,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-ap-71-350-71-apochromatische-refractor-redcat-wifd\/","url_meta":{"origin":33717,"position":4},"title":"William Optics AP 71\/350 71 Apochromatic Refractor RedCat WIFD OTA","author":"","date":"14-11-2025","format":false,"excerpt":"This is just the tube (OTA), without mounting and tripod. You can choose the appropriate mounting and the accessories that come with it below. William Optics RedCat 71 WIFD: Petzval-apochromate 71\/350 f\/4.9 with internal WIFD focus. Flat, color-pure image up to full-frame. Supplied with Bahtinov mask, Arca\/Vixen dovetail and carrying case.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-AP-71-350-71-Apochromatische-refractor-RedCat-WIFD-9.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":33684,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-ap-71-350-71-apochromatische-refractor-redcat-ota\/","url_meta":{"origin":33717,"position":5},"title":"William Optics AP 71\/350 71 Apochromatic Refractor RedCat OTA","author":"","date":"14-11-2025","format":false,"excerpt":"This is just the tube (OTA), without mounting and tripod. You can choose the appropriate mounting and the accessories that come with it below. William Optics RedCat 71: Petzval achromatic 71\/350 f\/4.9 with flat image to full-frame. Supplied with Bahtinov mask in the lens cap, Vixen\/Arca owl tail and carrying case.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-AP-71-350-71-Apochromatische-refractor-RedCat-OTA-14.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]}],"_links":{"self":[{"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product\/33717","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/types\/product"}],"replies":[{"embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/comments?post=33717"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/media\/97249"}],"wp:attachment":[{"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/media?parent=33717"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_brand?post=33717"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_cat?post=33717"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_tag?post=33717"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}