{"product_id":"starlight-instruments-3-5-diameter-riser-adds-3-35-to-length","title":"Starlight Instruments 3.5\" Diameter Riser, Adds 3.35\" to Length","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eExtends optical path by 3.35\" (85 mm)\u003c\/li\u003e\n\u003cli\u003eDesigned for 3.5\" diameter Feather Touch focusers\u003c\/li\u003e\n\u003cli\u003eFits all FTF35xx series focusers\u003c\/li\u003e\n\u003cli\u003eThreads directly onto the focuser draw tube for maximum rigidity\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\u003eStarlight Instruments 3.5\" Diameter Riser, Adds 3.35\" to Length\u003c\/h2\u003e\n\u003cp\u003eThe Starlight Instruments 3.5\" Diameter Riser provides a critical 3.35\" (85 mm) of additional length for all FTF35xx Feather Touch focusers. It threads directly onto the 3.5\" focuser's draw tube, consuming backfocus to bring imaging trains or eyepieces with long optical paths into the focuser's range of travel.\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\u003eAdd 3.35\" of Extension to Your 3.5\" Feather Touch Focuser\u003c\/h3\u003e\n\u003cp\u003eThis component is a precision-machined spacer designed for a single purpose: to extend the optical path of a 3.5\" Feather Touch focuser by exactly 3.35\" (85 mm). If your imaging train, binoviewer, or specific eyepiece combination places the focal plane beyond the maximum outward travel of your FTF35xx focuser, this riser provides the necessary mechanical extension to achieve a sharp focus.\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\u003eSolving Focus Travel Issues with a 3.35\" Riser\u003c\/h3\u003e\n\u003cp\u003eEngineered to integrate perfectly with Starlight Instruments hardware, this 3.5\" riser is not a generic extension tube. It threads directly onto the focuser's draw tube, sitting securely below the end cap to create a solid, flex-free connection. This rigid assembly ensures that even heavy camera packages maintain perfect alignment, preventing tilt that can compromise image quality.\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 problem does the Starlight Instruments 3.5\" Riser solve?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis 3.35\" riser solves the problem of having insufficient outward focuser travel. Certain accessories, like some cameras, off-axis guiders, or binoviewers, require the focal point to be positioned far away from the telescope tube. If this distance is greater than your focuser's draw tube can extend, you won't be able to achieve focus. The riser adds a fixed 3.35\" of length, pushing your eyepiece or camera back to a point where the focuser can reach the focal plane.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow do I install the 3.35\" Riser on my FTF35xx focuser?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eInstallation is straightforward. First, you unthread and remove the end cap (e.g., the 2\" compression ring adapter) from your 3.5\" Feather Touch focuser's draw tube. Then, you thread the riser directly onto the now-exposed draw tube threads. Finally, you thread your original end cap onto the end of the riser.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill this 3.5\" riser introduce any flex into my imaging train?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo. The Starlight Instruments riser is machined from solid aluminum with precision threads that match the FTF35xx focuser perfectly. This ensures a rigid, secure connection that becomes an integral part of the focuser assembly, preventing tilt and flex even with heavy loads.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use this 3.5\" riser with a 2\" or 2.5\" Feather Touch focuser?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this riser is specifically designed for the \u003cstrong\u003e3.5\" diameter FTF35xx series\u003c\/strong\u003e of Feather Touch focusers. It will not fit focusers with smaller diameter draw tubes.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eI'm trying to use a binoviewer with my large refractor and FTF35xx focuser, but I can't reach focus. Is this 3.35\" riser the right solution?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eIt is very likely the correct solution. Binoviewers have a very long optical path and typically require significant outward focus travel. If you run out of travel on your FTF35xx focuser, adding this 3.35\" riser will provide the extra length needed to bring the eyepieces into focus.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eMy custom imaging train on my Ritchey-Chrétien telescope places the sensor too far away from the FTF35xx focuser to reach focus. Will this 3.35\" riser help?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. This is a classic use case for a riser. When a combination of accessories like an adaptive optics unit, filter wheel, and camera creates an imaging train that is too \"long,\" the focal plane is pushed far out. The 3.35\" riser bridges that gap, allowing your FTF35xx focuser's drawtube to bring the camera sensor to a point of sharp focus.\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\u003eDiameter\u003c\/td\u003e\n\u003ctd\u003e3.5\"\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAdded Length\u003c\/td\u003e\n\u003ctd\u003e3.35\" (85 mm)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompatibility\u003c\/td\u003e\n\u003ctd\u003eAll FTF35xx Feather Touch focusers\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMounting\u003c\/td\u003e\n\u003ctd\u003eThreads onto the draw tube, below the end cap\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\"\u003e3.5\" Riser (3.35\" Length)\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\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/starlight-instruments-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eStarlight Instruments 2-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Starlight Instruments","offers":[{"title":"Default Title","offer_id":52948910539037,"sku":"SI-R35-3.35","price":150.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/StarlightInstruments-R35-3-35-Riser-3-5-Diameter-adds-3-35-to-Length-1_ea66f11e-f63a-4935-9538-e215ae3aeefc.jpg?v=1789658807","url":"https:\/\/davidastro.com\/fr-us\/products\/starlight-instruments-3-5-diameter-riser-adds-3-35-to-length","provider":"David Astro","version":"1.0","type":"link"}