{"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":"2026-05-18T16:10:45","modified_gmt":"2026-05-18T14:10:45","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 91\/540 Refractor APO Space Gray OTA"},"content":{"rendered":"<h3 class=\"wp-block-heading\">Compact power, razor-sharp images<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The <strong>William Optics AP 91\/540 FluoroStar<\/strong> shows stars as dots.It <strong>triplet of FPL-53 and lanthanum glass<\/strong> delivers sharp images and pure colors.Double stars are clearly visible separately.Jupiter and Saturn reveal fine details as if you were close by.<\/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 aligncenter 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 AP 91\/540 frontal view OTA with removable lens cap and Losmandy dovetail\" class=\"wp-image-33785\" title=\"\"><\/figure>\n<\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">Lots of light, large field of view<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The <strong>91 mm opening<\/strong> Captures a lot of light for bright deep-sky and planetary observations.With the <strong>Flat6AIII flattener<\/strong> you get a flat image field, even on full-frame cameras.Astrophotography becomes easier and faster, with an even image all the way to the edge.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Accurate focusing, even with heavy equipment<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The <strong>rack-and-pinion focuser<\/strong> works smoothly and precisely.The <strong>1:10 reduction<\/strong> Helps you focus perfectly.The focuser is <strong>rotating<\/strong>, so your camera is always in the right position.The <strong>Bahtinov mask<\/strong> Makes focusing easy even for faint stars.<\/p>\n\n\n\n<figure class=\"wp-block-gallery has-nested-images columns-default is-cropped wp-block-gallery-2 is-layout-flex wp-block-gallery-is-layout-flex\">\n<figure class=\"wp-block-image aligncenter size-large\"><img decoding=\"async\" data-id=\"33786\" src=\"https:\/\/www.telescoop.nl\/wp-content\/uploads\/2025\/11\/William-Optics-AP-91-540-Apochromatische-refractor-Space-Gray-OTA-3.jpg\" alt=\"William Optics AP 91\/540 side view OTA with dew cap and focuser collapsed in detail\" class=\"wp-image-33786\" title=\"\"><\/figure>\n<\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">Lightweight and travel friendly<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The <strong>retractable dew cap<\/strong> Makes the tube compact for transportation.With <strong>4.16 kg<\/strong> take it with you easily when traveling.The telescope has a sturdy handle and Vixen\/Skywatcher accessory shoe.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Ideal for astrophotography and planets<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Perfect for detailed shots of planets, nebulae and galaxies.Suitable for advanced and compact observatories.<\/p>\n\n\n\n<h1 class=\"wp-block-heading\"><strong>Specifications<\/strong><\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Optics<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Feature<\/th><th>Description<\/th><\/tr><\/thead><tbody><tr><td>Type<\/td><td>Refractor<\/td><\/tr><tr><td>Design<\/td><td>Apochromat<\/td><\/tr><tr><td>Aperture (mm)<\/td><td>91<\/td><\/tr><tr><td>Focal length (mm)<\/td><td>540<\/td><\/tr><tr><td>Focal Ratio (f\/)<\/td><td>5,9<\/td><\/tr><tr><td>Resolution<\/td><td>1,52\u2033<\/td><\/tr><tr><td>Limit value (mag)<\/td><td>12,3<\/td><\/tr><tr><td>Light output<\/td><td>170<\/td><\/tr><tr><td>Max. useful magnification<\/td><td>182\u00d7<\/td><\/tr><tr><td>Lens Design<\/td><td>Triplet<\/td><\/tr><tr><td>Tube weight (kg)<\/td><td>4,16<\/td><\/tr><tr><td>Tube diameter (mm)<\/td><td>100<\/td><\/tr><tr><td>Tube length (mm)<\/td><td>510<\/td><\/tr><tr><td>Transport length (mm)<\/td><td>441<\/td><\/tr><tr><td>Coating<\/td><td>STM<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">Focuser<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Feature<\/th><th>Description<\/th><\/tr><\/thead><tbody><tr><td>Design<\/td><td>Rack-and-pinion<\/td><\/tr><tr><td>Ocular connection<\/td><td>2\u2033<\/td><\/tr><tr><td>Connection (camera side)<\/td><td>T2<\/td><\/tr><tr><td>Reduction<\/td><td>1:10 finesse<\/td><\/tr><tr><td>Rotatable<\/td><td>Yes<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">Mount<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Feature<\/th><th>Description<\/th><\/tr><\/thead><tbody><tr><td>Design<\/td><td>OTA<\/td><\/tr><tr><td>Type of mount<\/td><td>Without<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">Included accessories<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Section<\/th><th>Description<\/th><\/tr><\/thead><tbody><tr><td>Divergent optics<\/td><td>No<\/td><\/tr><tr><td>Dovetail<\/td><td>Losmandy-Style<\/td><\/tr><tr><td>Handle<\/td><td>Yes<\/td><\/tr><tr><td>Focusing aid<\/td><td>Bahtinov mask<\/td><\/tr><tr><td>Transport bag<\/td><td>Yes<\/td><\/tr><tr><td>Accessory shoe<\/td><td>Vixen\/Skywatcher Level<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">General<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Feature<\/th><th>Description<\/th><\/tr><\/thead><tbody><tr><td>Series<\/td><td>FluoroStar<\/td><\/tr><tr><td>Color<\/td><td>Silver<\/td><\/tr><tr><td>Observation goals<\/td><td>Astrophotography, Moon &amp; Planets, Nebulae &amp; galaxies, Sun (with filter)<\/td><\/tr><tr><td>Recommended for<\/td><td>Advanced<\/td><\/tr><tr><td>Observatory use<\/td><td>Yes<\/td><\/tr><\/tbody><\/table><\/figure>","protected":false},"excerpt":{"rendered":"<p>William Optics AP 91\/540 comes with retractable dew cap, Bahtinov focus mask, Losmandy swallowtail, sturdy handle, 1:10 rack-and-pinion focuser and deluxe transport bag - ideal for sharp visual observation and astrophotography. \u00a0<\/p>","protected":false},"featured_media":97298,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false},"product_brand":[643],"product_cat":[51,3175,567],"product_tag":[],"class_list":["post-33784","product","type-product","status-publish","has-post-thumbnail","product_brand-william-optics","product_cat-telescopen","product_cat-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":105023,"url":"https:\/\/www.telescoop.nl\/en\/levenhuk-blitz-50-base\/","url_meta":{"origin":33784,"position":0},"title":"Levenhuk Blitz 50 BASE \u2013 50\/600 Refractor","author":"Abdullah Ibrar","date":"01-04-2026","format":false,"excerpt":"The Levenhuk Blitz 50 BASE \u2013 50\/600 Refractor comes with 6mm and 20mm eyepieces, a 3x Barlow lens, a 5x24 finder scope, a diagonal mirror, and an aluminum tripod. This user-friendly beginner telescope is ideal for observing the Moon, bright objects, and simple daytime nature observation.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"Levenhuk Blitz 50 BASE achromatic refractor on a fully extended aluminum tripod, showing the complete setup from the front.","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/77098_levenhuk-blitz-50-base-telescope_00.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/77098_levenhuk-blitz-50-base-telescope_00.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/77098_levenhuk-blitz-50-base-telescope_00.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/77098_levenhuk-blitz-50-base-telescope_00.jpg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/77098_levenhuk-blitz-50-base-telescope_00.jpg?resize=1050%2C600&ssl=1 3x"},"classes":[]},{"id":105495,"url":"https:\/\/www.telescoop.nl\/en\/levenhuk-new-skyline-pro-16\/","url_meta":{"origin":33784,"position":1},"title":"Levenhuk New Skyline PRO 16\u2033 \u2013 406\/1830 Dobson","author":"Abdullah Ibrar","date":"03-04-2026","format":false,"excerpt":"The Levenhuk New Skyline PRO 16\" \u2013 406\/1830 Dobson comes with 10 mm and 25 mm Pl\u00f6ssl eyepieces, an 8x40 optical finderscope, and a primary mirror cooling system. This very powerful telescope is ideal for observing the Moon, planets, and extremely detailed deep-sky objects.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"Levenhuk New Skyline PRO 16 inch main setup with optical tube on Dobsonian mount","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/86287_levenhuk-new-skyline-pro-16-telescope_00_500_465f630cb432cbffc2c1740e1897afbc.webp?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":106246,"url":"https:\/\/www.telescoop.nl\/en\/levenhuk-discovery-spark-767-az\/","url_meta":{"origin":33784,"position":2},"title":"Levenhuk Discovery Spark 767 AZ \u2013 76\/700 Newtonian Reflector","author":"Abdullah Ibrar","date":"05-04-2026","format":false,"excerpt":"The Levenhuk Discovery Spark 767 AZ \u2013 76\/700 Newtonian reflector comes with SR4mm, H12.5mm, and H20mm eyepieces, a 2x Barlow lens, an optical finder, an aluminum tripod with an accessory tray, and the colorful knowledge book \u201cSpace. Not an Empty Void.\u201d Ideal for beginners who want to discover the Moon, planets, and deep-sky objects.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"Levenhuk Discovery Spark 767 AZ complete set met Newton-reflector op alt-azimut montering en aluminium statief op witte achtergrond","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/79071_discovery-spark-767-az-telescope_00_500_8a8d4daec6536c85fe839f5bcbed1b02.webp?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":104875,"url":"https:\/\/www.telescoop.nl\/en\/levenhuk-labzz-t3\/","url_meta":{"origin":33784,"position":3},"title":"Levenhuk LabZZ T3 - 60\/700 Refractor","author":"Abdullah Ibrar","date":"24-03-2026","format":false,"excerpt":"Levenhuk LabZZ T3 - 60\/700 Refractor comes with 4mm eyepiece, 12.5mm eyepiece, 1.5x eyepiece, 3x Barlow lens, 5x optical viewfinder, zenith mirror and aluminum tripod with accessory tray.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"Levenhuk LabZZ T3 - 60\/700 Refractor aluminium statief met accessoirebak","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/03\/Levenhuk-LabZZ-T3-60700-Refractor-1.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":105543,"url":"https:\/\/www.telescoop.nl\/en\/levenhuk-skyline-travel-70\/","url_meta":{"origin":33784,"position":4},"title":"Levenhuk Skyline Travel 70 - 70\/400 Refractor","author":"Abdullah Ibrar","date":"03-04-2026","format":false,"excerpt":"The Levenhuk Skyline Travel 70 \u2013 70\/400 Refractor comes with 10mm and 20mm eyepieces, a 3x Barlow lens, a 5x24 finderscope, a diagonal prism, an aluminum tripod, and a backpack. This compact travel telescope is ideal for observing the Moon, bright planets, and nature.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"Levenhuk Skyline Travel 70 compact refractor with included backpack for easy transportation","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/levenhuk-telescope-skyline-travel-70_ZHSMksd_500_784c0dc006013c7ff5ad43e1c4c51569.webp?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":107590,"url":"https:\/\/www.telescoop.nl\/en\/televue-oculairtas-transporttas\/","url_meta":{"origin":33784,"position":5},"title":"TeleVue Oculairtas \u2013 Carrying Case","author":"Abdullah Ibrar","date":"28-04-2026","format":false,"excerpt":"TeleVue Oculairtas \u2013 transporttas wordt geleverd met stevige foamvoering en biedt ruimte aan maximaal 13 oculairs en accessoires.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"TeleVue Transporttas Oculairtas gesloten grijze nylon oculairtas met handgrepen, ritssluiting en schouderriem op witte achtergrond","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/TeleVue-Transporttas-Oculairtas-5.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/TeleVue-Transporttas-Oculairtas-5.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/TeleVue-Transporttas-Oculairtas-5.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2026\/04\/TeleVue-Transporttas-Oculairtas-5.jpg?resize=700%2C400&ssl=1 2x"},"classes":[]}],"_links":{"self":[{"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product\/33784","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=33784"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/media\/97298"}],"wp:attachment":[{"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/media?parent=33784"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_brand?post=33784"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_cat?post=33784"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/www.telescoop.nl\/en\/wp-json\/wp\/v2\/product_tag?post=33784"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}