{"id":15362,"date":"2025-07-06T19:45:39","date_gmt":"2025-07-06T17:45:39","guid":{"rendered":"https:\/\/www.telescoop.nl\/?post_type=product&#038;p=15362"},"modified":"2026-06-09T11:44:02","modified_gmt":"2026-06-09T09:44:02","slug":"zwo-ir-blocking-filter-d21","status":"publish","type":"product","link":"https:\/\/www.telescoop.nl\/en\/zwo-ir-blocking-filter-d21\/","title":{"rendered":"ZWO IR-blocking filter D21"},"content":{"rendered":"<p class=\"wp-block-paragraph\"><strong>ZWO IR-blocking filter D21<\/strong> is a special interference filter that blocks unwanted infrared light and protects your ZWO ASI camera from dust and moisture. For refractors, this filter prevents focus shift between visible and IR light, leading to sharper images. For reflecting telescopes, a clear glass filter is sufficient, but with the IR blocker you are ready for all conditions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Key benefits<\/strong><br>\u2713 90 % transmission in visible light for brightness without color transition<br>\u2713 IR-blocking coating prevents blur caused by IR focus shift<br>\u2713 Protects sensor from dust, moisture and scratches during long sessions<br>\u2713 Loose D21 filter fits directly into M42 filter wheels or camera mount<br>\u2713 Interference technology minimizes reflections and preserves contrast<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Practical application<\/strong><br>Screw this filter as the first element in your filter wheel or directly on the camera to eliminate IR light leaks. Use with refractors for maximum sharpness and keep your sensor clean. Combined with narrowband or color filters improves overall image sharpness and color fidelity.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Technical specifications<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Format: loose D21 filter (M42 \u00d7 0.75)<\/li>\n\n\n\n<li>Type: IR-blocking interference filter<\/li>\n\n\n\n<li>Transmission: 90 % in visible spectrum<\/li>\n\n\n\n<li>Coating: multi-layer anti-reflection<\/li>\n\n\n\n<li>Glass thickness: 2 mm<\/li>\n\n\n\n<li>Application: narrowband and broadband astrophotography (photographic)<\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"<p data-start=\"1679\" data-end=\"1747\">\u00a0<\/p>\n<p data-start=\"1491\" data-end=\"1677\">ZWO IR-blocking filter D21 protects your ASI camera and blocks infrared for razor-sharp, high-contrast shots. 90 % transmission, M42 loose design.<\/p>","protected":false},"featured_media":21118,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false},"product_brand":[123],"product_cat":[3136,588,56],"product_tag":[],"class_list":["post-15362","product","type-product","status-publish","has-post-thumbnail","product_brand-zwo","product_cat-correctiefilters-uv-ir-cut","product_cat-filters","product_cat-telescoop-accessoires","product_shipping_class-licht","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":15365,"url":"https:\/\/www.telescoop.nl\/en\/zwo-ir-blocking-filter-d25\/","url_meta":{"origin":15362,"position":0},"title":"ZWO IR-blocking filter D25","author":"","date":"06-07-2025","format":false,"excerpt":"\u00a0 ZWO IR-blocking filter D25 for ASI cameras. Blocks infrared, protects sensor and provides 90 % transmission for razor-sharp, high-contrast images.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"ZWO IR-Sperrfilter D25","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Blocking-filters-IR-ASI-D25.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Blocking-filters-IR-ASI-D25.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Blocking-filters-IR-ASI-D25.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Blocking-filters-IR-ASI-D25.jpg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Blocking-filters-IR-ASI-D25.jpg?resize=1050%2C600&ssl=1 3x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Blocking-filters-IR-ASI-D25.jpg?resize=1400%2C800&ssl=1 4x"},"classes":[]},{"id":15337,"url":"https:\/\/www.telescoop.nl\/en\/zwo-helderglasfilter-d21\/","url_meta":{"origin":15362,"position":1},"title":"ZWO Clear Glass Filter D21","author":"","date":"05-07-2025","format":false,"excerpt":"\u00a0 ZWO Clear Glass Filter D21 for ASI Cameras. Protect your sensor from dust and moisture with 95 % transmission with no image loss.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"ZWO Klarglasfilter D21","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D21.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D21.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D21.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D21.jpg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D21.jpg?resize=1050%2C600&ssl=1 3x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D21.jpg?resize=1400%2C800&ssl=1 4x"},"classes":[]},{"id":15341,"url":"https:\/\/www.telescoop.nl\/en\/zwo-helderglasfilter-d25\/","url_meta":{"origin":15362,"position":2},"title":"ZWO Clear Glass Filter D25","author":"","date":"05-07-2025","format":false,"excerpt":"\u00a0 ZWO Clear Glass Filter D25 for ASI cameras - 95 % transmission and reliable sensor protection without image loss.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"ZWO Klarglasfilter D25","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D25.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D25.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D25.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D25.jpg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D25.jpg?resize=1050%2C600&ssl=1 3x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/07\/ZWO-Filters-Helderglasfilter-ASI-D25.jpg?resize=1400%2C800&ssl=1 4x"},"classes":[]},{"id":14833,"url":"https:\/\/www.telescoop.nl\/en\/zwo-blocking-filters-uv-ir-125\/","url_meta":{"origin":15362,"position":3},"title":"ZWO Blocking Filters UV\/IR 1.25\u2033","author":"","date":"23-06-2025","format":false,"excerpt":"The ZWO Blocking Filters UV\/IR 1.25\" block infrared and ultraviolet light for sharper and colorfast astrophotos with color cameras and 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\/06\/ZWO-Blocking-filters-UV-IR-1-25-.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/06\/ZWO-Blocking-filters-UV-IR-1-25-.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/06\/ZWO-Blocking-filters-UV-IR-1-25-.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/06\/ZWO-Blocking-filters-UV-IR-1-25-.jpg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/06\/ZWO-Blocking-filters-UV-IR-1-25-.jpg?resize=1050%2C600&ssl=1 3x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/06\/ZWO-Blocking-filters-UV-IR-1-25-.jpg?resize=1400%2C800&ssl=1 4x"},"classes":[]},{"id":25245,"url":"https:\/\/www.telescoop.nl\/en\/omegon-blocking-filter-infraroodfilter-125\/","url_meta":{"origin":15362,"position":4},"title":"Omegon Blocking Filter Infrared Filter 1.25\u2033","author":"","date":"07-08-2025","format":false,"excerpt":"\u00a0 Omegon Blocking Filter Infrared Filter 1.25\" - blocks unwanted IR radiation in photography and visual observation, for sharper images and better color correction.","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"Omegon Blocking Filter Infraroodfilter 1,25\"","src":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/08\/Omegon-Blocking-filters-Infrared-band-elimination-filter.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/08\/Omegon-Blocking-filters-Infrared-band-elimination-filter.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/08\/Omegon-Blocking-filters-Infrared-band-elimination-filter.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/08\/Omegon-Blocking-filters-Infrared-band-elimination-filter.jpg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/08\/Omegon-Blocking-filters-Infrared-band-elimination-filter.jpg?resize=1050%2C600&ssl=1 3x, https:\/\/i0.wp.com\/www.telescoop.nl\/wp-content\/uploads\/2025\/08\/Omegon-Blocking-filters-Infrared-band-elimination-filter.jpg?resize=1400%2C800&ssl=1 4x"},"classes":[]},{"id":15348,"url":"https:\/\/www.telescoop.nl\/en\/zwo-lrgb-filterset-36-mm-losse-filters\/","url_meta":{"origin":15362,"position":5},"title":"ZWO LRGB filter set 36 mm separate filters","author":"","date":"06-07-2025","format":false,"excerpt":"\u00a0 ZWO LRGB filter set 36 mm separate filters for ZWO cameras. 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