{"id":33664,"date":"2025-11-14T12:34:15","date_gmt":"2025-11-14T11:34:15","guid":{"rendered":"https:\/\/www.telescoop.nl\/?post_type=product&#038;p=33664"},"modified":"2026-09-10T14:45:34","modified_gmt":"2026-09-10T12:45:34","slug":"william-optics-ap-51-250-apochromatic-refractor-spacecat-wifd-ota","status":"publish","type":"product","link":"https:\/\/www.telescoop.nl\/en\/william-optics-ap-51-250-apochromatische-refractor-spacecat-wifd-ota\/","title":{"rendered":"William Optics AP 51\/250 Apochromatic Refractor SpaceCat WIFD OTA"},"content":{"rendered":"<h2 class=\"wp-block-heading has-text-align-center\"><strong>The same Cat optics in its own design<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The <strong>William Optics SpaceCat 51 WIFD<\/strong> It shares its optical heart with the RedCat 51: the same fast f\/4.9 Petzval system, the same internal WIFD focuser, but in the distinctive SpaceCat version. You get a bright, flat image that remains sharp all the way to the corners, even on full-frame.<\/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=\"33667\" src=\"https:\/\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-AP-51250-Apochromatische-refractor-SpaceCat-WIFD-OTA-2.jpg\" alt=\"William Optics SpaceCat 51 WIFD apochromatic astrograph, full image\" class=\"wp-image-33667\" 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-SpaceCat-WIFD-OTA-10.jpg\" alt=\"The SpaceCat 51 WIFD with dovetail bar and Bahtinov mask\" class=\"wp-image-33675\" 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\">Ready for the tracker<\/h4>\n\n\n\n<p class=\"wp-block-paragraph\">The Petzval design makes a separate flattener redundant, so your setup stays light and simple: tube, camera, tracker, done. The Arca-Swiss\/Vixen dovetail bar fits directly onto photo tripods and star trackers, and the integrated Bahtinov mask makes focusing exact and fast.<\/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>SpaceCat 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> (version for the Cat 51 WIFD) the SpaceCat can also be used visually. 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 the proven Cat 51 optics and prefer the SpaceCat version's aesthetics or appreciate the price advantage. Not: those looking for a longer focal length for smaller objects; the RedCat 71 or Cat 91 class provides a larger image scale.<\/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 SpaceCat 51 WIFD: the same f\/4.9 Petzval optics as the RedCat 51 in the SpaceCat version, featuring an internal focuser. Supplied with a Bahtinov mask, dovetail bar, and carrying case.<\/p>","protected":false},"featured_media":97204,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false},"product_brand":[643],"product_cat":[51,428,3175,567],"product_tag":[],"class_list":["post-33664","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","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":[34142,15860,33941,33946,34295],"acf":[],"jetpack_sharing_enabled":true,"jetpack-related-posts":[{"id":111636,"url":"https:\/\/www.telescoop.nl\/en\/zwo-seestar-s50-pro\/","url_meta":{"origin":33664,"position":0},"title":"ZWO Seestar S50 Pro","author":"Info telescoop","date":"25-08-2026","format":false,"excerpt":"De ZWO Seestar S50 Pro is de opvolger van de Seestar S50: 50 mm quadruplet APO (260 mm, f\/5.2), twee 4K-sensoren van 8,3 MP, een groothoekcamera van 63 graden voor de Melkweg tot 8K, drie ingebouwde filters, 10.000 mAh accu (tot 9 uur) en 128 GB opslag. 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