{"id":34297,"date":"2025-11-17T18:26:31","date_gmt":"2025-11-17T17:26:31","guid":{"rendered":"https:\/\/www.telescoop.nl\/?post_type=product&#038;p=34297"},"modified":"2026-08-25T15:11:45","modified_gmt":"2026-08-25T13:11:45","slug":"william-optics-flt91-flat6a-iii-special-edition","status":"publish","type":"product","link":"https:\/\/www.telescoop.nl\/en\/william-optics-flt91-flat6a-iii-special-edition\/","title":{"rendered":"William Optics FLT91 Flat6A III Special Edition"},"content":{"rendered":"<h2 class=\"wp-block-heading has-text-align-center\"><strong>William Optics FLT91 Flat6A III Special Edition: custom-calculated for the FluoroStar 91<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">This Special Edition of the Flat6AIII is specifically calculated for the William Optics FluoroStar FLT91. Every refractor naturally produces a slightly curved image field; a flat camera sensor cuts through this, causing stars in the corners to stretch into streaks. A flattener corrects for this curvature so that stars remain small and round all the way to the corners. Especially with a fast triplet like the FLT91 (around f\/5 to f\/7) and large sensors, a custom-calculated flattener is the difference between good and tight corners.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The flattener mounts via the 2-inch connection of the FLT91 and comes with a camera adapter featuring a fixed, pre-calculated back focus distance: the sensor is thus positioned directly at the correct spot, without measuring or spacer rings.<\/p>\n\n\n\n<figure class=\"wp-block-gallery has-nested-images columns-3 is-cropped wp-block-gallery-1 is-layout-flex wp-block-gallery-is-layout-flex\"><figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-FLT91-Flat6A-III-Special-Edition.jpg\" alt=\"William Optics Flat6AIII Special Edition for FLT91\" title=\"\"><\/figure><\/figure>\n\n\n\n<h4 class=\"wp-block-heading\">Why a dedicated flattener per telescope<\/h4>\n\n\n\n<p class=\"wp-block-paragraph\">Field curvature varies per optical design. A universal flattener provides average correction; this edition corrects the curvature of the FLT91 precisely.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Featured accessories<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Connect your camera using the included adapter and your camera's T2 ring or M48 adaptermerk.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">For whom yes and for whom no<\/h3>\n\n\n\n<ul class=\"wp-block-list\"><li>\u2713 Owners of a FluoroStar FLT91 who do astrophotography<\/li><li>\u2717 Owners of other WO apos: choose the flattener calculated for your model<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Specifications<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><strong>Type<\/strong><\/td><td>Field flattener, specially calculated<\/td><\/tr><tr><td><strong>Suitable for<\/strong><\/td><td>William Optics FluoroStar FLT91<\/td><\/tr><tr><td><strong>Telescope silk<\/strong><\/td><td>2-inch connection<\/td><\/tr><tr><td><strong>Included<\/strong><\/td><td>Camera adapter with fixed flange focal distance<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">You can find more accessories for this brand at the <a href=\"\/en\/brands\/william-optics\/\">William Optics brand page<\/a>.<\/p>","protected":false},"excerpt":{"rendered":"<p>William Optics Flat6AIII Special Edition for the FluoroStar 91: specially calculated flattener with 2-inch connection and included camera adapter with fixed flange focal distance.<\/p>","protected":false},"featured_media":97649,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false},"product_brand":[643],"product_cat":[56,469,3105,3104],"product_tag":[],"class_list":["post-34297","product","type-product","status-publish","has-post-thumbnail","product_brand-william-optics","product_cat-telescoop-accessoires","product_cat-astro-fotografie","product_cat-optische-accessoires","product_cat-overige-astrofotografie-accessoires","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":34228,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-flat6a-iii-reducer-flattener-adjustable-2-inch\/","url_meta":{"origin":34297,"position":0},"title":"William Optics Flat6A III Reducer Flattener Adjustable 50.8 mm","author":"","date":"17-11-2025","format":false,"excerpt":"William Optics Flat6AIII adjustable flattener-reducer 0.8x: Ohara glass, M63 telescope side, M48 camera side, 48mm filter thread and distance scale. For GT71, GT81, Z81, Z103 and f\/6 to f\/7.5 refractors.","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-Flat6AIII-Reducer-Flattener-Adjustable-1.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":33784,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-91-540-refractor-apo-space-gray-ota\/","url_meta":{"origin":34297,"position":1},"title":"William Optics Fluorostar 91\/540 Refractor APO Space Gray OTA","author":"","date":"14-11-2025","format":false,"excerpt":"This is just the tube (OTA), without the mounting and tripod. You can choose the appropriate mounting and the accessories that come with it below. William Optics Fluorostar 91 Space Gray: FPL-53 apochromatic triplet 91\/540 f\/5.9 with lanthanum glass and 1:10 focuser. Supplied with dew cap, Losmandy-owl-tail mount, handle, Bahtinov mask and luxury 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-91-540-Apochromatische-refractor-Space-Gray-OTA-2.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":33971,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-6a-adapters-voor-flattener\/","url_meta":{"origin":34297,"position":2},"title":"William Optics 6A Adapters for Flattener\u00a0","author":"","date":"15-11-2025","format":false,"excerpt":"William Optics 6A adapter from M92 to M63: threaded, tilt-free coupling for the Flat6A and Flat6A III flatteners.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":33973,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-flat68ii-flat7a-adapter\/","url_meta":{"origin":34297,"position":3},"title":"William Optics Flat68II Flat7A Adapter\u00a0","author":"Info telescoop","date":"15-11-2025","format":false,"excerpt":"William Optics 45 mm adapter between the Flat68II or Flat7A flattener and your T2-ring: exact correct sensor distance for a flat field of view.","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-Flat68II-Flat7A-Adapter-1.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":114062,"url":"https:\/\/www.telescoop.nl\/en\/uittrekbuisadapter-voor-de-william-optics-flat4-veldvlakker-william-optics\/","url_meta":{"origin":34297,"position":4},"title":"Extension tube adapter for the William Optics Flat4 field viewer | William Optics","author":"Info telescoop","date":"09-10-2026","format":false,"excerpt":"Connect the Flat4 field flattener from William Optics with the extension tube of your focus lens for stars that stay in focus right to the corners.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/88211_1.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/88211_1.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/88211_1.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":34085,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-flat61r-61-field-flattener-zenithstar\/","url_meta":{"origin":34297,"position":5},"title":"William Optics Flat61R 61 Field Flattener for ZenithStar","author":"Info telescoop","date":"16-11-2025","format":false,"excerpt":"William Optics Flat61R flattener for the ZenithStar 61 and GuideStar 61: adjustable M54 connection, M48 camera side, and integrated M48 filter thread. Round stars all the way to the corners.","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-Flat61R-61-Beeldveldegalisator-voor-ZenithStar-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\/34297","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=34297"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/media\/97649"}],"wp:attachment":[{"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/media?parent=34297"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_brand?post=34297"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_cat?post=34297"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_tag?post=34297"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}