{"product_id":"optolong-clear-focusing-filter","title":"Optolong Clear Focusing Filter","description":"\u003ch2\u003eOptolong Clear Focusing Filter\u003c\/h2\u003e\n\u003cp\u003eOptolong Clear focusing filter is designed to highly pass the visible spectral region 420-680nm at 98.5% transmission.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eMain Use\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eUse of astrophotography filters, especially narrowband filters, often results in dim images which can be difficult to focus. Clear focusing filter can be used first to clearly focus the image.\u003c\/p\u003e\n\u003cp\u003eUse with modified DSLRs for higher efficiency and sensitivity by passing visible range with 98.5% transmission.\u003c\/p\u003e\n\u003cp\u003eAct as an outstanding dust shield, which prevents the possibility of dust settling on the lens during long time exposure.\u003c\/p\u003e\n\u003cp\u003eWARNING: The filters of Optolong are not designed for sun observation. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTER. You would be BLIND if you fail to observe the warning.\u003c\/p\u003e\n\u003ch3\u003eTechnical Specifications  \u003c\/h3\u003e\n\u003cp\u003e\u003cspan\u003eSbustrate: B270\u003c\/span\u003e\u003cbr\u003e\u003cspan\u003eThickness: 1.85mm\u003c\/span\u003e\u003cbr\u003e\u003cspan\u003eTave:  T\u0026gt;98.5%\u003c\/span\u003e\u003cbr\u003e\u003cspan\u003eSurface quality: 60\/40\u003c\/span\u003e\u003cbr\u003e\u003cspan\u003eTransmitted Wavefront RMS: λ\/4\u003c\/span\u003e\u003cbr\u003e\u003cspan\u003eParallelism: 30s\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003e\u003cimg src=\"https:\/\/optolong.com\/uploads\/images\/20201125\/17144ed49cbdafca3c8e855b1129a71a.png\" width=\"499\" height=\"326\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eHow to read the chart?\u003c\/p\u003e\n\u003cp\u003e▲The horizontal axis is the Wavelength in Nanometers(nm).\u003c\/p\u003e\n\u003cp\u003e▲The vertical axis is transmission in %.\u003c\/p\u003e\n\u003ch3 data-mce-fragment=\"1\"\u003eIn the Box\u003cbr data-mce-fragment=\"1\"\u003e\n\u003c\/h3\u003e\n\u003cp data-mce-fragment=\"1\"\u003e\u003cspan\u003eFilter\u003c\/span\u003e\u003c\/p\u003e\n\u003ch3 data-mce-fragment=\"1\"\u003eManual \u0026amp; Warranty\u003c\/h3\u003e\n\u003cp\u003e\u003cbr\u003e\u003c\/p\u003e","brand":"Optolong","offers":[{"title":"1.25\"","offer_id":43693144277221,"sku":"OPT-CF-1.25","price":33.0,"currency_code":"CAD","in_stock":true},{"title":"2\"","offer_id":43693144309989,"sku":"OPT-CF-2","price":41.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/optolong-clear-focusing-filter-astronomy-plus_123750df-9a37-44c8-92bc-1e7d6597d016.png?v=1690487288","url":"https:\/\/istronomyplus.com\/products\/optolong-clear-focusing-filter","provider":"Astronomy Plus – Telescopes \u0026 Astrophotography Canada","version":"1.0","type":"link"}