{"product_id":"explore-scientific-es-foc3-bc100127t","title":"Explore Scientific 3-inch Self-Centering Focuser with Back Cell Adapter for White Tube ED127 and FCD-100","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eDesigned for Explore Scientific white-tube ED127 and FCD-100 refractors\u003c\/li\u003e\n\u003cli\u003e17 lb instrument lifting capacity\u003c\/li\u003e\n\u003cli\u003eSelf-centering compression system eliminates image shift and tilt\u003c\/li\u003e\n\u003cli\u003e9:1 dual-speed helical rack-and-pinion focuser\u003c\/li\u003e\n\u003cli\u003e84.5mm of drawtube travel\u003c\/li\u003e\n\u003cli\u003e14 internal baffles for enhanced contrast\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\u003eDownloads\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\u003e3-inch Self-Centering Focuser with Back Cell Adapter for White Tube ED127 and FCD-100\u003c\/h2\u003e\n\u003cp\u003eThis 3-inch Self-Centering Focuser upgrades Explore Scientific's white-tube ED127 and FCD-100 refractors with a heavy-duty drawtube capable of lifting a 17 lb imaging train without flexure or image shift. The 9:1 dual-speed helical rack-and-pinion mechanism, running on stainless steel ball bearings, provides 84.5mm of precise travel, while 14 internal baffles ensure maximum contrast. Its self-centering compression system eliminates image shift, securing 2-inch and 3-inch accessories via a robust M82x1.25 thread.\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\u003e17 lb Capacity and 9:1 Precision: A Focuser for Heavy Imaging Trains\u003c\/h3\u003e\n\u003cp\u003eModern imaging systems require a focuser that can handle substantial weight without compromise. With a 17 lb lifting capacity, this focuser is engineered to support full-frame cameras, heavy filter wheels, and off-axis guiders without sagging or slipping. The robust helical rack-and-pinion design, supported by stainless steel ball bearings, ensures smooth and repeatable motion across its full 84.5mm of travel. The 9:1 dual-speed control allows you to make the micro-adjustments necessary to achieve critical focus, especially when imaging at high resolution.\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\u003eZero-Tilt Self-Centering Mechanism with 14 Internal Baffles\u003c\/h3\u003e\n\u003cp\u003eThe core of this focuser's optical stability is its self-centering compression system. Unlike simple thumbscrews that can push an accessory off-axis, this mechanism applies even pressure around the circumference of your diagonal or camera nosepiece. This guarantees a perfectly centered optical train, eliminating the tilt that can ruin corner star performance. To further enhance image quality, the drawtube is lined with 14 internal baffles that trap stray light, increasing contrast and preventing internal reflections from degrading faint detail.\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\u003eDirect Fit for ED127 \u0026amp; FCD-100: M82x1.25 Connectivity\u003c\/h3\u003e\n\u003cp\u003eThis version of the 3-inch focuser is built specifically for owners of Explore Scientific's popular white-tube ED127 and FCD-100 series refractors. The included back cell adapter is threaded for a direct, secure connection to these optical tubes, making it a seamless, bolt-on upgrade. On the accessory side, the focuser terminates in a standard M82x1.25 female thread, providing a solid connection point for larger field flatteners, reducers, and other 3-inch imaging accessories.\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 is the main advantage of the Explore Scientific 3-inch Self-Centering Focuser over a standard Crayford?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe primary advantage is the combination of its \u003cstrong\u003ehelical rack-and-pinion drive\u003c\/strong\u003e and \u003cstrong\u003eself-centering mechanism\u003c\/strong\u003e. While a Crayford relies on friction, the rack-and-pinion provides a positive, slip-free engagement capable of handling a 17 lb load. The self-centering system also eliminates the possibility of tilt and image shift common with simple compression rings or thumbscrews.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill this 3-inch focuser fit my Explore Scientific ED127 Carbon Fiber model?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this specific model is designed exclusively for the \u003cstrong\u003ewhite-tube versions of the ED127 and FCD-100 series\u003c\/strong\u003e telescopes. The threading on the included back cell adapter will not match the carbon fiber or other Explore Scientific models. You would need the base ES-FOC3 model and a different adapter for other telescopes.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the 17 lb lifting capacity of this ES focuser benefit my astrophotography with an ED127?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA typical imaging train for an ED127—including a field flattener, off-axis guider, filter wheel, and a cooled astronomy camera—can easily exceed 10 pounds. The \u003cstrong\u003e17 lb capacity\u003c\/strong\u003e of this focuser ensures that your entire setup is held rigidly in place, even when the telescope is pointed near the zenith. This prevents focus drift and mechanical flexure during a long exposure, resulting in sharper stars across the entire frame.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat accessories can I connect to the M82x1.25 thread on this focuser?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe \u003cstrong\u003eM82x1.25 thread\u003c\/strong\u003e is a common standard for larger format imaging accessories. You can directly thread on:\n\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e3-inch field flatteners and focal reducers designed for this thread pitch.\u003c\/li\u003e\n\u003cli\u003eAdapters that step down to other common sizes, like M68, M54, or M48, for connecting smaller correctors or camera systems.\u003c\/li\u003e\n\u003cli\u003e3-inch extension tubes for achieving the correct back focus distance.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDoes the self-centering mechanism on the ES 3-inch Focuser prevent my camera from rotating?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe self-centering mechanism is designed to hold your equipment securely and eliminate tilt, but it does not act as a rotational lock. For precise framing of your target, you will still need to manually set the camera's rotation before fully tightening the compression ring.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI want to image the faint dust lanes in the Andromeda Galaxy (M31) with my FCD-100. How do the 14 internal baffles help?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhen imaging a large, faint object like the Andromeda Galaxy (M31), maximizing contrast is critical. Off-axis light from bright stars or skyglow can enter the optical tube and cause internal reflections, washing out faint details. The \u003cstrong\u003e14 knife-edge baffles\u003c\/strong\u003e inside the focuser's drawtube act as light traps, absorbing this stray light before it reaches your camera sensor. This results in a darker background sky and makes subtle details like the dust lanes in M31 more visible.\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\u003eFocuser Design\u003c\/td\u003e\n\u003ctd\u003e3-inch Helical Rack-and-Pinion\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocus Ratio\u003c\/td\u003e\n\u003ctd\u003e9:1 Dual-Speed\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLifting Capacity\u003c\/td\u003e\n\u003ctd\u003e17 lb\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDrawtube Travel\u003c\/td\u003e\n\u003ctd\u003e84.5mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eClamping Mechanism\u003c\/td\u003e\n\u003ctd\u003eSelf-centering compression system (zero tilt, zero image shift)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eInternal Baffles\u003c\/td\u003e\n\u003ctd\u003e14\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBearings\u003c\/td\u003e\n\u003ctd\u003eStainless steel ball bearings\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAccessory Connection\u003c\/td\u003e\n\u003ctd\u003eM82x1.25 female thread\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTelescope Compatibility\u003c\/td\u003e\n\u003ctd\u003eExplore Scientific white-tube ED127 and FCD-100 series\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\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003e3-inch Self-Centering Focuser with Back Cell Adapter for ED127\/FCD-100\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Explore_Scientific_PMC-Eight_Precision_Motion_Controller_Manual.pdf\" target=\"_blank\"\u003e\u003csvg class=\"DAV-img-box\" viewbox=\"0 0 512 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"\u003e\u003cpath d=\"M0 64C0 28.7 28.7 0 64 0L224 0l0 128c0 17.7 14.3 32 32 32l128 0 0 144-208 0c-35.3 0-64 28.7-64 64l0 144-48 0c-35.3 0-64-28.7-64-64L0 64zm384 64l-128 0L256 0 384 128zM176 352l32 0c30.9 0 56 25.1 56 56s-25.1 56-56 56l-16 0 0 32c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-48 0-80c0-8.8 7.2-16 16-16zm32 80c13.3 0 24-10.7 24-24s-10.7-24-24-24l-16 0 0 48 16 0zm96-80l32 0c26.5 0 48 21.5 48 48l0 64c0 26.5-21.5 48-48 48l-32 0c-8.8 0-16-7.2-16-16l0-128c0-8.8 7.2-16 16-16zm32 128c8.8 0 16-7.2 16-16l0-64c0-8.8-7.2-16-16-16l-16 0 0 96 16 0zm80-112c0-8.8 7.2-16 16-16l48 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 32 32 0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-32 0 0 48c0 8.8-7.2 16-16 16s-16-7.2-16-16l0-64 0-64z\" fill=\"#0047a7\"\u003e\u003c\/path\u003e\u003c\/svg\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eDownload Manual\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/explore-scientific-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eExplore Scientific Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":52909312475421,"sku":"ES-FOC3-BC100127T","price":999.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/ExploreScientific-3-inch-Self-Centering-Focuser-with-Back-Cell-Adapter-for-White-Tube-ED127-and-FCD-100-1_f8c79c2c-9580-4f3f-bf67-0ee39e9d62e0.jpg?v=1789061195","url":"https:\/\/davidastro.com\/en-us\/products\/explore-scientific-es-foc3-bc100127t","provider":"David Astro","version":"1.0","type":"link"}