{"id":33659,"date":"2025-11-14T12:14:14","date_gmt":"2025-11-14T11:14:14","guid":{"rendered":"https:\/\/www.telescoop.nl\/?post_type=product&#038;p=33659"},"modified":"2026-07-18T13:21:03","modified_gmt":"2026-07-18T11:21:03","slug":"william-optics-ap-51-250-apochromatic-refractor-redcat-wifd","status":"publish","type":"product","link":"https:\/\/www.telescoop.nl\/en\/william-optics-ap-51-250-apochromatische-refractor-redcat-wifd\/","title":{"rendered":"William Optics AP 51\/250 Apochromatic Refractor RedCat WIFD OTA"},"content":{"rendered":"<h2 class=\"wp-block-heading has-text-align-center\"><strong>The most famous travel astrograph, now with internal focuser<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The <strong>William Optics RedCat 51 WIFD<\/strong> is the latest version of the world's most famous compact astrograph. The fast f\/4.9 optics allow for short exposures, and the image remains sharp to the edges, even on a full-frame camera.<\/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=\"33660\" src=\"https:\/\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-AP-51250-Apochromatische-refractor-RedCat-WIFD-1.jpg\" alt=\"William Optics RedCat 51 WIFD Apochromatic Astrograph, Full Frame\" class=\"wp-image-33660\" 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-51250-Apochromatische-refractor-RedCat-WIFD-3.jpg\" alt=\"The RedCat 51 WIFD with integrated Bahtinov mask\" class=\"wp-image-33662\" 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\">Petzval optics plus WIFD focuser<\/h4>\n\n\n\n<p class=\"wp-block-paragraph\">The four-element Petzval system with FPL53 and FPL51 glass provides a flat, color-pure image without a separate flattener: stars remain round and sharp, saving you time on post-processing. The internal WIFD focuser maintains constant balance and prevents sagging under camera weight. The Bahtinov mask is integrated into the lens cap.<\/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>RedCat 51\/250 Optical Tube with WIFD Focuser<\/li>\n\n\n\n<li>Integrated Bahtinov mask<\/li>\n\n\n\n<li>Arca-Swiss &amp; Vixen-Style Prism Rail<\/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\">With the <a href=\"https:\/\/www.telescoop.nl\/en\/william-optics-90-125-zenith-prism-redcat\/\">William Optics 90 degree zenith prism<\/a> (for the Cat 51 WIFD) do you also use the RedCat visually and for nature observation with an upright image. A <a href=\"https:\/\/www.telescoop.nl\/en\/telescope-accessories\/astro-photography\/other-astrophotography-accessories\/\">William Optics UniGuide 32mm Guidescope<\/a> (159 euros) completes the setup for long exposures. William Optics' M48 camera adapters are available for common mounts; choose the variant for your camera.<\/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\">For: Astrophotographers who want a proven, color-pure astrograph that fits on any star tracker. Not for: Those primarily interested in visual observation; this is a photography tube. The ZenithStar line is more versatile.<\/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, four-lens Petzval (FPL53 and FPL51)<\/td><\/tr><tr><td>Opening<\/td><td>51 mm<\/td><\/tr><tr><td>Focal length<\/td><td>250 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>Field of view<\/td><td>Flat to full-frame<\/td><\/tr><tr><td>Focus assist<\/td><td>Integrated Bahtinov mask<\/td><\/tr><tr><td>Attachment<\/td><td>Arca-Swiss and Vixen-Style<\/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>William Optics RedCat 51 WIFD: the most famous compact astrograph with a four-element Petzval optical design (FPL53\/FPL51) and internal focuser. Flat, color-corrected image up to full-frame. Delivered with Bahtinov mask, prism rail, and carrying bag.<\/p>","protected":false},"featured_media":97199,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false},"product_brand":[643],"product_cat":[51,428,531,3175,567],"product_tag":[],"class_list":["post-33659","product","type-product","status-publish","has-post-thumbnail","product_brand-william-optics","product_cat-telescopen","product_cat-telescopen-voor-astrofotografie","product_cat-gevorderd","product_cat-refractor-ota","product_cat-refractor-telescopen","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":[],"acf":[],"jetpack_sharing_enabled":true,"jetpack-related-posts":[{"id":33664,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-ap-51-250-apochromatische-refractor-spacecat-wifd-ota\/","url_meta":{"origin":33659,"position":0},"title":"William Optics AP 51\/250 Apochromatic Refractor SpaceCat WIFD OTA","author":"","date":"14-11-2025","format":false,"excerpt":"William Optics SpaceCat 51 WIFD: dezelfde f\/4,9 Petzval-optiek als de RedCat 51 in de SpaceCat-uitvoering, met interne focuser. Geleverd met Bahtinov-masker, prismabalk en draagtas.","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":33699,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-ap-71-350-71-apochromatische-refractor-redcat-wifd\/","url_meta":{"origin":33659,"position":1},"title":"William Optics AP 71\/350 71 Apochromatic Refractor RedCat WIFD OTA","author":"","date":"14-11-2025","format":false,"excerpt":"William Optics RedCat 71 WIFD: Petzval-apochromaat 71\/350 f\/4,9 met interne WIFD-focuser. Vlak, kleurzuiver beeld tot full-frame. Geleverd met Bahtinov-masker, Arca\/Vixen-zwaluwstaart en draagtas.","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":33729,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-redcat-91-448-apo-wifd-red-ota\/","url_meta":{"origin":33659,"position":2},"title":"William Optics RedCat 91\/448 APO WIFD Red OTA","author":"","date":"14-11-2025","format":false,"excerpt":"William Optics RedCat 91 WIFD: Petzval-apochromaat 91\/448 f\/4,9 in de rode uitvoering, met M48\/M54-adapters en interne focuser. Geleverd met zwaluwstaartstang, Bahtinov-masker en draagtas.","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":34142,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-90-125-zenitprisma-cat-51-wifd\/","url_meta":{"origin":33659,"position":3},"title":"William Optics 90\u00b0 1.25\" Zenith prism Cat 51 WIFD","author":"","date":"17-11-2025","format":false,"excerpt":"William Optics 90 graden zenitprisma voor de Cat 51 WIFD: dielektrisch gecoat BaK-4 prisma met 2 naar 1,25 inch adapter en ringklem. Rechtopstaand beeld voor natuur en maan.","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-90%C2%B0-125-Zenitprisma-Cat-51-WIFD-2.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":33659,"position":4},"title":"William Optics AP 71\/350 71 Apochromatic Refractor RedCat OTA","author":"","date":"14-11-2025","format":false,"excerpt":"William Optics RedCat 71: Petzval-apochromaat 71\/350 f\/4,9 met vlak beeld tot full-frame. Geleverd met Bahtinov-masker in de objectiefdop, Vixen\/Arca-zwaluwstaart en draagtas.","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":[]},{"id":33652,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-ap-51-178-apochromatische-refractor-minicat-wifd-ota\/","url_meta":{"origin":33659,"position":5},"title":"William Optics AP 51\/178 Apochromatic refractor MiniCat WIFD OTA","author":"","date":"14-11-2025","format":false,"excerpt":"William Optics MiniCat 51\/178 WIFD: ultra-compact f\/3.5 apochromat with internal focuser for wide-field astrophotography. Supplied with Bahtinov mask, dew shield, 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-51178-Apochromatische-refractor-MiniCat-WIFD-OTA-1.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]}],"_links":{"self":[{"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product\/33659","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=33659"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/media\/97199"}],"wp:attachment":[{"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/media?parent=33659"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_brand?post=33659"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_cat?post=33659"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_tag?post=33659"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}