{"product_id":"askar-0-74x-reducer-for-131f","title":"Askar 131F 0.74× Reducer","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eReduces telescope focal ratio to f\/5.6\u003c\/li\u003e\n\u003cli\u003eAchieves a 733.6mm final focal length\u003c\/li\u003e\n\u003cli\u003eTriplet optical design for field flattening\u003c\/li\u003e\n\u003cli\u003eStandard 55mm back focus from the M48 thread\u003c\/li\u003e\n\u003cli\u003eWeighs 0.56kg\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eAskar 131F 0.74× Reducer\u003c\/h2\u003e\n\u003cp\u003eThe Askar 131F 0.74x Reducer converts the Askar 131F refractor into a faster f\/5.6 astrograph with a final focal length of 733.6mm. This dedicated triplet reducer provides a wider field of view and significantly shortens exposure times, all while maintaining a precise 55mm back focus distance and weighing just 0.56kg.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003e0.74x Reduction: Transforming the 131F to an f\/5.6 Astrograph\u003c\/h3\u003e\n\u003cp\u003eBy reducing the native f\/7.5 optics of the Askar 131F to a faster f\/5.6, this reducer cuts required exposure times by nearly half. This speed is critical for capturing faint details in nebulae and galaxies. The triplet optical design doesn't just reduce the focal length to 733.6mm; it also flattens the field, ensuring stars remain sharp and round across a full-frame sensor from the center to the corners of your image.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eMechanical Design: 55mm Back Focus and Full-Frame Correction\u003c\/h3\u003e\n\u003cp\u003eEngineered for seamless integration, the reducer maintains the industry-standard 55mm back focus distance, measured from the base of its M48 male thread. This simplifies the process of connecting your DSLR, mirrorless, or dedicated astronomy camera with standard adapters and off-axis guiders. The main body features a rear-end M72x1 thread for a secure connection to the telescope's focuser, and the CNC-machined housing ensures precise optical alignment.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does the Askar 131F 0.74× Reducer do to my telescope's focal length?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe 0.74x Reducer shortens the Askar 131F's native focal length to \u003cstrong\u003e733.6mm\u003c\/strong\u003e and speeds up the focal ratio from f\/7.5 to \u003cstrong\u003ef\/5.6\u003c\/strong\u003e. This provides a wider field of view and gathers light more quickly, reducing your total imaging time.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the back focus of the Askar 131F 0.74× Reducer?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe required back focus is \u003cstrong\u003e55mm\u003c\/strong\u003e, measured from the base of the male M48 thread on the reducer. This is a standard distance that works directly with most DSLR cameras using a T-ring and many dedicated astronomy camera setups.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow will the Askar 131F 0.74× Reducer help me image the Andromeda Galaxy (M31)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Andromeda Galaxy is a very large target. The reducer's \u003cstrong\u003e733.6mm\u003c\/strong\u003e focal length provides a wider field of view, allowing you to capture the entire galaxy and its faint outer arms within a single frame using a full-frame or APS-C sensor. The faster \u003cstrong\u003ef\/5.6\u003c\/strong\u003e optics will also help you capture more signal in less time.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the Askar 131F 0.74× Reducer suitable for imaging large nebulae like the North American Nebula (NGC 7000)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eAbsolutely. The wide field of view provided by the \u003cstrong\u003e733.6mm\u003c\/strong\u003e focal length is ideal for framing large emission nebulae like NGC 7000. Furthermore, the fast \u003cstrong\u003ef\/5.6\u003c\/strong\u003e focal ratio is highly effective at capturing faint hydrogen-alpha signal, making it a perfect match for such targets.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat kind of optical correction does the Askar 131F 0.74× Reducer provide?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe reducer uses a \u003cstrong\u003etriplet lens design\u003c\/strong\u003e. This multi-element configuration is engineered not only to reduce the focal length but also to act as a field flattener, correcting for the natural field curvature of the main optics. This ensures that stars are sharp across the entire imaging sensor.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow much does the Askar 131F 0.74× Reducer weigh?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe reducer weighs \u003cstrong\u003e0.56kg\u003c\/strong\u003e. This is an important consideration for ensuring your mount remains properly balanced after adding the reducer and camera to the optical train.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eReduction Factor\u003c\/td\u003e\n\u003ctd\u003e0.74x\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eReduced Focal Length\u003c\/td\u003e\n\u003ctd\u003e733.6mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eReduced Focal Ratio\u003c\/td\u003e\n\u003ctd\u003ef\/5.6\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLens Design\u003c\/td\u003e\n\u003ctd\u003eTriplet\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBack Focus\u003c\/td\u003e\n\u003ctd\u003e55mm (from the base of M48 male thread)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e0.56kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRear-end Thread\u003c\/td\u003e\n\u003ctd\u003eM72x1\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/askar-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eAskar 1-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Askar","offers":[{"title":"Default Title","offer_id":52851337429277,"sku":"ASK-ASKAR131FRD","price":299.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Askar-131F-0-74-Reducer-1_efb7cdda-5cf2-46a8-a24c-8bb2c26ac7dd.jpg?v=1788401779","url":"https:\/\/davidastro.com\/en-us\/products\/askar-0-74x-reducer-for-131f","provider":"David Astro","version":"1.0","type":"link"}