{"id":33784,"date":"2025-11-14T16:12:58","date_gmt":"2025-11-14T15:12:58","guid":{"rendered":"https:\/\/www.telescoop.nl\/?post_type=product&#038;p=33784"},"modified":"2026-07-18T13:43:11","modified_gmt":"2026-07-18T11:43:11","slug":"william-optics-91-540-refractor-apo-space-gray-ota","status":"publish","type":"product","link":"https:\/\/www.telescoop.nl\/en\/william-optics-91-540-refractor-apo-space-gray-ota\/","title":{"rendered":"William Optics Fluorostar 91\/540 Refractor APO Space Gray OTA"},"content":{"rendered":"<h2 class=\"wp-block-heading has-text-align-center\"><strong>The compact Fluorostar: triplet quality in travel size<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The <strong>William Optics Fluorostar 91 Space Gray<\/strong> brings the Fluorostar triplet line to a compact, portable size. The triplet of FPL-53 and lanthanum glass shows stars as true points with pure colors: double stars clearly separated and fine details on Jupiter and Saturn.<\/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=\"33785\" src=\"https:\/\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-AP-91-540-Apochromatische-refractor-Space-Gray-OTA-1.jpg\" alt=\"William Optics Fluorostar 91 Space Gray apochromatic triplet refractor, full-frame\" class=\"wp-image-33785\" 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-91-540-Apochromatische-refractor-Space-Gray-OTA-3.jpg\" alt=\"The Fluorostar 91 with rack-and-pinion focuser and dew shield\" class=\"wp-image-33786\" 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\">Lots of light, large field of view<\/h4>\n\n\n\n<p class=\"wp-block-paragraph\">The 91mm aperture at a 540mm focal length (f\/5.9) combines light-gathering power with a generous field of view, suitable for both bright deep-sky images and high-contrast planetary observations. The 1:10 rack-and-pinion focuser achieves micron-level sharpness and can support a full camera rig. The retractable dew shield helps keep the lens clear for longer, and the deluxe carrying case offers protection during transport.<\/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 Fluorostar 91\/540 triplet, Space Gray<\/li>\n\n\n\n<li>Retractable lens hood<\/li>\n\n\n\n<li>1:10 rack-and-pinion focuser<\/li>\n\n\n\n<li>Losmandy dovetail<\/li>\n\n\n\n<li>Handle<\/li>\n\n\n\n<li>Bahtinov mask<\/li>\n\n\n\n<li>Luxury transport 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\">The <a href=\"https:\/\/www.telescoop.nl\/en\/telescope-accessories\/astro-photography\/other-astrophotography-accessories\/\">William Optics FLT91 Flat6A III Special Edition<\/a> (429 euros) is the exact matching flattener-reducer for this tube; the UniGuide 32 mm guidescope (159 euros) enables guided imaging.<\/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 Fluorostar triplet quality in a travel-friendly, light-mount-compatible package. Not for: those seeking maximum aperture for a fixed setup; the Fluorostar 120 or 132 will provide more light and resolution.<\/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, FPL-53 triplet with lanthanum glass<\/td><\/tr><tr><td>Opening<\/td><td>91 millimeters<\/td><\/tr><tr><td>Focal length<\/td><td>540 mm<\/td><\/tr><tr><td>Opening ratio<\/td><td>f\/5,9<\/td><\/tr><tr><td>Focuser<\/td><td>Rack and pinion with 1:10 fine adjustment<\/td><\/tr><tr><td>Dew cap<\/td><td>Retractable<\/td><\/tr><tr><td>Attachment<\/td><td>Losmandy dovetail with handle<\/td><\/tr><tr><td>Execution<\/td><td>OTA (loose tube), Space Gray<\/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 Fluorostar 91 Space Gray: FPL-53 triplet apochromat 91\/540 f\/5.9 with lanthanum glass and 1:10 focuser. Delivered with dew shield, Losmandy dovetail, handle, Bahtinov mask, and deluxe carrying case.<\/p>","protected":false},"featured_media":97298,"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-33784","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":33809,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-fluorostar-120-780-apo-space-gray-ota\/","url_meta":{"origin":33784,"position":0},"title":"William Optics Fluorostar 120\/780 APO Space Gray OTA","author":"","date":"14-11-2025","format":false,"excerpt":"William Optics Fluorostar 120 Space Gray: FPL-53 triplet apochromaat 120\/780 f\/6,5 met lanthaanglas. Geleverd met Losmandy-zwaluwstaart, handvat, accessoireschoen, Bahtinov-masker en transporttas.","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-120-780-Apochromatische-refractor-AP-Fluorostar-Space-Gray-OTA-2.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":33761,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-fluorostar-132-925-refractor-apo-space-gray-ota\/","url_meta":{"origin":33784,"position":1},"title":"William Optics Fluorostar 132\/925 Refractor APO Space Gray OTA","author":"","date":"14-11-2025","format":false,"excerpt":"William Optics Fluorostar 132 Space Gray: FPL-53 triplet apochromaat 132\/925 f\/7 met lanthaanglas en 3,7 inch rotatiefocuser. 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Supplied with Losmandy dovetail, handle, accessory shoe, 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-120-780-Apochromatische-refractor-AP-Fluorostar-Gold-OTA-3.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":33800,"url":"https:\/\/www.telescoop.nl\/en\/william-optics-fluorostar-120-780-apo-red-ota\/","url_meta":{"origin":33784,"position":4},"title":"William Optics Fluorostar 120\/780 APO Red OTA","author":"","date":"14-11-2025","format":false,"excerpt":"William Optics Fluorostar 120 Red: FPL-53 triplet apochromaat 120\/780 f\/6,5 met lanthaanglas. 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