{"id":114062,"date":"2026-10-09T16:58:36","date_gmt":"2026-10-09T14:58:36","guid":{"rendered":"https:\/\/www.telescoop.nl\/?post_type=product&#038;p=114062"},"modified":"2026-10-13T09:48:52","modified_gmt":"2026-10-13T07:48:52","slug":"extension-tube-adapter-for-the-william-optics-flat4-field-marker-william-optics","status":"publish","type":"product","link":"https:\/\/www.telescoop.nl\/en\/uittrekbuisadapter-voor-de-william-optics-flat4-veldvlakker-william-optics\/","title":{"rendered":"Extension tube adapter for the William Optics Flat4 field viewer | William Optics"},"content":{"rendered":"<p class=\"wp-block-paragraph\">Stars extending out in the corners of your photo often indicate image field curvature in your refractor. The Flat4 from William Optics blurs that field, and with this William Optics Flat4 adapter you connect the flat surface to the extension tube of your focus lens.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Which adapter you need depends on the telescope and the focusers. Check beforehand whether the thread and diameter of your extension tube match and whether the adapter is compatible with your telescope. You can find other adapters at <a href=\"https:\/\/www.telescoop.nl\/en\/telescope-accessories\/astro-photography\/other-astrophotography-accessories\/optical-accessories\/flatteners\/\">veldvlakkers for refractors<\/a>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Pay attention to the distance between the flat surface and the sensor. It must be correct; otherwise the stars at the edge will still be stretched out. Take a test image and especially look at the corners. If you have a 4-inch refractor from William Optics, this will help. <a href=\"https:\/\/www.telescoop.nl\/en\/bahtinov-mask-for-4-inch-william-optics-refractors-102-and-103-mm-william-optics\/\">a Bahtinov mask for 102 and 103 mm<\/a> when focusing.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If you are using a 3 inch focus lens, then there is <a href=\"https:\/\/www.telescoop.nl\/en\/transition-adapter-from-3-inch-female-to-william-optics-male-starlight\/\">a conversion adapter to William Optics<\/a>.<\/p>","protected":false},"excerpt":{"rendered":"<p>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.<\/p>","protected":false},"featured_media":114061,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false},"product_brand":[643],"product_cat":[499,56],"product_tag":[],"class_list":["post-114062","product","type-product","status-publish","has-post-thumbnail","product_brand-william-optics","product_cat-adapters","product_cat-telescoop-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":114065,"url":"https:\/\/www.telescoop.nl\/en\/adapters-voor-zwo-eaf-motorfocus-op-william-optics-telescopen-william-optics\/","url_meta":{"origin":114062,"position":0},"title":"Adapters for ZWO EAF motor focus on William Optics telescopes | William Optics","author":"Info telescoop","date":"09-10-2026","format":false,"excerpt":"Mounting adapters for a ZWO EAF focus motor on William Optics telescopes. This allows your recording software to set the focus without touching the telescope.","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\/89711_1.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/89711_1.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/89711_1.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":113655,"url":"https:\/\/www.telescoop.nl\/en\/focuseradapter-voor-william-optics-flt-35-inch-starlight\/","url_meta":{"origin":114062,"position":1},"title":"Focus adapter for William Optics FLT, 3.5 inch | Starlight","author":"Info telescoop","date":"09-10-2026","format":false,"excerpt":"Adapter to attach a 3.5 inch focuser from Starlight Instruments, such as a Feather Touch, to a William Optics FLT refractor.","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\/73954_1.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/73954_1.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/73954_1.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":113663,"url":"https:\/\/www.telescoop.nl\/en\/focuseradapter-voor-william-optics-gt102-3-inch-starlight\/","url_meta":{"origin":114062,"position":2},"title":"Focus adapter for William Optics GT102, 3 inch | Starlight","author":"Info telescoop","date":"09-10-2026","format":false,"excerpt":"With this you can mount a 3 inch focuser from Starlight Instruments on a William Optics GT102, with room for larger cameras and accessories.","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\/74105_1.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/74105_1.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/74105_1.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":113594,"url":"https:\/\/www.telescoop.nl\/en\/focuseradapter-voor-william-optics-megrez-90-past-op-feather-touch-2-inch-starlight\/","url_meta":{"origin":114062,"position":3},"title":"Focus adapter for William Optics Megrez 90, fits Feather Touch 2 inch | Starlight","author":"Info telescoop","date":"09-10-2026","format":false,"excerpt":"2 inch adapter to mount a Feather Touch focuser from Starlight Instruments on a William Optics Megrez 90 refractor.","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\/46448_1.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/46448_1.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/46448_1.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":113623,"url":"https:\/\/www.telescoop.nl\/en\/focuseradapter-voor-william-optics-66-mm-refractor-past-op-feather-touch-starlight\/","url_meta":{"origin":114062,"position":4},"title":"Focus adapter for William Optics 66 mm refractor, fits Feather Touch | Starlight","author":"Info telescoop","date":"09-10-2026","format":false,"excerpt":"Adapter to attach a Feather Touch focus from Starlight Instruments to a small William Optics refractor of 66 mm.","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\/49136_1.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/49136_1.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/49136_1.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":113661,"url":"https:\/\/www.telescoop.nl\/en\/overgangsadapter-van-3-inch-female-naar-william-optics-male-starlight\/","url_meta":{"origin":114062,"position":5},"title":"Transition adapter from 3 inch female to William Optics male | Starlight","author":"Info telescoop","date":"09-10-2026","format":false,"excerpt":"Extension piece from Starlight Instruments with 3 inch inner thread to William Optics outer thread, so that parts from both brands fit together.","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\/74104_1.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/74104_1.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/10\/74104_1.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]}],"_links":{"self":[{"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product\/114062","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=114062"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/media\/114061"}],"wp:attachment":[{"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/media?parent=114062"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_brand?post=114062"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_cat?post=114062"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_tag?post=114062"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}