{"product_id":"takahashi-fs-60cp-60mm-f-5-9-fluorite-doublet-apochromatic-refractor-ota","title":"Takahashi FS-60CP 60mm f\/5.9 Fluorite Doublet Apochromatic Refractor OTA","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe FS-60CP is Takahashi's fixed-tube 60 mm fluorite doublet apochromat, built around the same objective as the FS-60CB but housed in a longer, 95 mm-diameter tube with a permanently mounted camera angle adjuster. At 355 mm focal length and f\/5.9 it shares the CB's optical formula and most of its conversion-lens options, but the longer tube gives it 197.8 mm of back focus at prime focus — well over the CB's 162 mm — which is what lets it run Takahashi's newer FU-series reducer without running out of drawtube travel. Attach the 60CP FURD 0.65x reducer and it becomes a 230 mm f\/3.8 astrograph.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThis is a good match if you already know you want a wide-field imaging platform and would rather buy the longer-backfocus tube outright than add a spacer later. It suits imagers running the FU reducer for fast, flat fields, and anyone assembling a permanent imaging rig rather than a travel kit that gets reconfigured on site. It is less suited to observers who want the shortest, most collapsible package — the FS-60CB's retractable dew shield is the better fit there.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eAir-spaced fluorite doublet:\u003c\/strong\u003e the same two-element, two-group objective used in the FS-60CB — a genuine fluorite crystal element, not an ED-glass substitute.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e355 mm at f\/5.9:\u003c\/strong\u003e 60 mm aperture, native prime-focus figures identical to the CB.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e197.8 mm of back focus:\u003c\/strong\u003e a fixed 95 mm tube gives substantially more rear clearance than the CB's 162 mm, built for reducer and flattener use.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCamera angle adjuster:\u003c\/strong\u003e built into the rear cell, for rotating framing without disturbing focus.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e63 mm drawtube extension\u003c\/strong\u003e on a rack-and-pinion focuser.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.8 kg:\u003c\/strong\u003e heavier than the CB by the length of tube, still light for most imaging mounts.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe objective is the same two-element, air-spaced fluorite doublet used across the FS-60 line — fluorite's anomalous partial dispersion pulls the red, green and blue focal points close enough together that a two-element design performs like a more complex triplet at this aperture, without the violet fringing that limits ordinary short achromats. Hard multicoatings protect the fluorite surface and cut internal reflections.\u003c\/p\u003e\u003cp\u003eWhat distinguishes the CP from the CB is the tube itself, not the glass. The 95 mm barrel is fixed rather than telescoping, and the extra length shifts the back focus out to 197.8 mm at prime focus — room enough for the 60CP FURD 0.65x reducer to reach focus, a part specified for this tube's back focus and not interchangeable with the CB's reducer. Takahashi notes that focus to infinity is not available in the base configuration without the correct diagonal or extension in the visual train, worth checking against the eyepiece setup you plan to use.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFast wide-field imaging:\u003c\/strong\u003e with the 60CP FURD 0.65x reducer at 230 mm and f\/3.8, for large nebulae and wide star fields.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFlat-field imaging at prime focus:\u003c\/strong\u003e with the FC\/FS MFL 1.04x flattener at 370 mm and f\/6.2, corrected across a 44 mm circle.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReduced-field imaging:\u003c\/strong\u003e with the 60C RD NC 0.85x reducer at 300 mm and f\/5.0.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVisual observing:\u003c\/strong\u003e lunar, double-star and wide-field work with a diagonal and eyepiece, keeping the infinity-focus note above in mind.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe FS-60CB and FS-60CP share the flattener and 0.85x reducer, but the 60CP FURD 0.65x reducer is built specifically for the CP's longer back focus and is a different part from the CB's reducer. Our \u003ca href=\"\/pages\/takahashi-back-focus-guide\"\u003eTakahashi Back Focus Guide\u003c\/a\u003e lists the figures for both tubes side by side, which is the fastest way to confirm a train before ordering.\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eBack focus:\u003c\/strong\u003e 197.8 mm at prime focus.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eField flattener:\u003c\/strong\u003e FC\/FS MFL 1.04x — 370 mm, f\/6.2, 44 mm circle, 87.5 mm back focus.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFocal reducer:\u003c\/strong\u003e 60C RD NC 0.85x — 300 mm, f\/5.0, 44 mm circle, 56.0 mm back focus.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFU reducer:\u003c\/strong\u003e 60CP FURD 0.65x — 230 mm, f\/3.8, 44 mm circle, 56.0 mm back focus measured from the rear of the adapter.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMount:\u003c\/strong\u003e sold as an OTA — no mount, rings or dovetail included.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eIf you are not sure which reducer or CA ring your camera needs, send us your camera and filter setup and we will work it out with you.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eThis is an optical tube assembly.\u003c\/strong\u003e Mount, tripod, rings, dovetail, diagonal, eyepiece and finder are sold separately.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFocus to infinity needs the right visual train.\u003c\/strong\u003e Takahashi notes the base configuration does not reach infinity focus without the correct extension tube or diagonal in place — worth checking against the eyepiece or diagonal you plan to use.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThe CP's FU reducer is model-specific.\u003c\/strong\u003e The 60CP FURD 0.65x is built for this tube's back focus and is a different part from the CB's reducer.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eA flat field needs a corrector.\u003c\/strong\u003e At prime focus the field curves; the flattener or reducer corrects it.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eNo — at prime focus it is a diagonal and eyepiece, or a camera and the appropriate spacer. The one detail worth checking ahead of time is the visual train reaching infinity focus, which depends on the diagonal or extension used; tell us your setup and we will confirm it.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is the difference between the FS-60CB and FS-60CP?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eSame objective and focal length, different tube. The CP's fixed 95 mm barrel gives 197.8 mm of back focus against the CB's 162 mm, and that extra room is what the FU reducer needs to reach focus.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is it best used for?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eWide-field imaging, particularly with the FU reducer at f\/3.8, where the extra back focus over the CB matters most.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes it need a flattener for astrophotography?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eAt prime focus, yes, for a flat field to the edge — the MFL 1.04x flattener or the 0.85x\/0.65x reducers each correct it differently.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I use FS-60CB accessories on this tube?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eThe flattener and 0.85x reducer are shared. The FU reducer is specific to the CP's back focus and is a separate part from the CB's reducer.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eIn short: a 60 mm fluorite apochromat at 355 mm and f\/5.9, built into a fixed 95 mm tube with 197.8 mm of back focus for reducer and flattener work — and a 230 mm f\/3.8 astrograph once the FU reducer is attached.\u003c\/p\u003e","brand":"Takahashi","offers":[{"title":"Default Title","offer_id":54047051382895,"sku":"TAK-TSK06410","price":1415.7,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/tsk06410-1.jpg?v=1786911768","url":"https:\/\/ontariotelescope.com\/products\/takahashi-fs-60cp-60mm-f-5-9-fluorite-doublet-apochromatic-refractor-ota","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}