{"product_id":"takahashi-mewlon-180c-180mm-f-12-dall-kirkham-ota-with-dovetail-plate","title":"Takahashi Mewlon-180C 180mm f\/12 Dall-Kirkham OTA with Dovetail Plate","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe Mewlon-180C is Takahashi's 180 mm Dall-Kirkham Cassegrain, sold here as an optical tube assembly with a D-series dovetail plate included. At 2160 mm focal length and f\/12 in a 625 mm tube, it packs long-focus resolving power into a 210 mm-diameter body that weighs 6.2 kg. The concave ellipsoidal primary and spherical secondary form the image with no corrector in the light path, and focusing is done by moving the primary mirror itself rather than by a rack-and-pinion drawtube.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThis is a good match if you want a compact, long-focal-length instrument for high-resolution planetary, lunar and double-star observing — the Dall-Kirkham design holds coma to a minimum across the visual field, so images stay sharp to the edge at high power. It also suits imagers working on small- and medium-sized targets — planetary nebulae, galaxy cores, the Moon and planets — where 2160 mm or, with the M-FLRD reducer, 1760 mm at f\/9.8 gives the reach a wide-field refractor cannot.\u003c\/p\u003e\u003cp\u003eIf your interest is nebulae and wide Milky Way fields, a fast refractor covers that ground better than this tube's native focal length. Tell us what you are imaging and we can confirm whether the 180C or a shorter instrument fits your target list.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eDall-Kirkham Cassegrain optics:\u003c\/strong\u003e a concave ellipsoidal primary paired with a spherical secondary — simpler to figure accurately than a hyperbolic Ritchey-Chrétien secondary, with negligible coma on-axis.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2160 mm at f\/12:\u003c\/strong\u003e in a 625 mm tube, 210 mm across — a long native focal length in a body short enough to carry to a dark site.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrimary-mirror focusing:\u003c\/strong\u003e the focal point moves by translating the primary, extending the back focal length by about 130 mm rather than relying on drawtube travel.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e6.2 kg:\u003c\/strong\u003e light for a 180 mm Cassegrain, within reach of mid-weight equatorial mounts once a diagonal or camera is added.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eD-series dovetail plate included:\u003c\/strong\u003e mounts directly to a compatible saddle without a separate plate purchase.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e67.2 mm of back focus\u003c\/strong\u003e at prime focus, measured from the rear of the 50.8 mm adapter.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eDall-Kirkham optics use a concave ellipsoidal primary and a spherical secondary rather than the hyperbolic primary and secondary of a Ritchey-Chrétien. The spherical secondary is easier to figure to a high standard, and on-axis coma stays low enough that visual observers rarely notice it. Off-axis field curvature is the tradeoff — the design suits the narrow, high-magnification field a planetary or lunar observer actually uses, rather than a wide, flat astrograph field.\u003c\/p\u003e\u003cp\u003eTakahashi focuses the Mewlon by moving the primary mirror rather than by extending a drawtube, which keeps the optical path sealed against dust and airflow disturbance during focusing. The M-FLRD focal reducer\/flattener brings the system to 1760 mm at f\/9.8 with a 30 mm corrected image circle and 56.2 mm of back focus — useful for imaging where the native f\/12 field is narrower than the sensor calls for.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eLunar and planetary observing:\u003c\/strong\u003e at 2160 mm and f\/12, high magnification with minimal coma.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDouble star splitting:\u003c\/strong\u003e the long focal length and central obstruction ratio favour close, faint pairs.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOccultation timing:\u003c\/strong\u003e a stable, long-focus platform for precise event capture.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSmall- and medium-target imaging:\u003c\/strong\u003e galaxy cores and planetary nebulae at native focal length, or at 1760 mm and f\/9.8 with the M-FLRD reducer for a 30 mm corrected circle.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eBack focus at prime is 67.2 mm from the rear of the 50.8 mm adapter — narrower than most apochromatic refractors, so a camera train with a long nosepiece or filter drawer may not reach focus without adjustment. Fitting the M-FLRD reducer changes that figure to 56.2 mm. Our \u003ca href=\"\/pages\/takahashi-back-focus-guide\"\u003eTakahashi Back Focus Guide\u003c\/a\u003e collects these figures for the whole Takahashi range in one table, and the Downloads tab below carries the Mewlon-180C's own system chart with the exact parts and distances for each configuration.\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFinder:\u003c\/strong\u003e Takahashi specifies a 6x30 finder for this tube; a compatible bracket and finder are separate purchases unless noted otherwise at checkout.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDovetail:\u003c\/strong\u003e the included D-series plate fits a Vixen-style or compatible saddle directly.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReducer\/flattener:\u003c\/strong\u003e the M-FLRD is sold separately and is the only listed conversion accessory for this tube.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMount:\u003c\/strong\u003e sold as an OTA with dovetail plate — no mount, diagonal or eyepiece included. At 6.2 kg plus accessories, a mid-weight equatorial mount rated for 8–10 kg of total payload is a reasonable starting point.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eIf you are not sure your camera's back focus reaches 67.2 mm, send us your imaging train and we will work out the spacing 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 The dovetail plate is included; mount, diagonal, eyepiece and finder are sold separately.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBack focus is tighter than a typical refractor.\u003c\/strong\u003e At 67.2 mm from the 50.8 mm adapter, some camera and diagonal combinations need a shorter adapter stack — the system chart in the Downloads tab lists the parts for each configuration.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNative field is narrow.\u003c\/strong\u003e At f\/12, the corrected field suits planetary and lunar targets rather than wide nebulae; the M-FLRD reducer widens the field to a 30 mm circle at f\/9.8.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCollimation is occasional maintenance, not a setup step.\u003c\/strong\u003e Like any Cassegrain it can drift with transport, and a collimation eyepiece brings it back into alignment.\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. It arrives collimated from the factory, and because focusing moves the primary mirror rather than a drawtube, there is no separate focuser mechanism to adjust before first light. Occasional collimation touch-ups are normal maintenance for any Cassegrain and are quick with a collimation eyepiece.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is it best used for?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eHigh-resolution lunar and planetary observing, double star splitting, and long-focal-length imaging of small targets — galaxy cores, planetary nebulae, occultation events.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes it come with a mount?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eNo. It ships as an optical tube assembly with the D-series dovetail plate. The plate fits a compatible saddle directly, but the mount itself is a separate purchase.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat cameras and accessories does it need for imaging?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eAny camera reaching the 67.2 mm back focus at prime, or 56.2 mm with the M-FLRD reducer fitted. Send us your camera and filter setup and we will confirm the spacing before you order.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow is this different from the Mewlon-210?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eAperture and resolving power. The 210 has a larger primary and a longer focal length; the 180C is lighter and more portable at a slightly smaller aperture.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhen should this not be the choice?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eFor wide-field nebula or Milky Way imaging, where a fast, short-focal-length refractor covers the frame this tube's narrower field cannot.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eIn short: a 180 mm Dall-Kirkham Cassegrain OTA at 2160 mm and f\/12 — 1760 mm at f\/9.8 with the M-FLRD reducer — weighing 6.2 kg and shipping with a D-series dovetail plate. It is built for long-focal-length resolution on the Moon, planets and double stars, with 67.2 mm of back focus to work into an imaging train.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eOptical Diagram Reports\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eTakahashi publishes a spot diagram for the Mewlon-180C at prime focus, showing star images across the field at the design wavelengths.\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/Mewlon-180C_spots.png?v=1786911644\" alt=\"Takahashi Mewlon-180C 180mm Dall-Kirkham spot diagram at prime focus\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e","brand":"Takahashi","offers":[{"title":"Default Title","offer_id":54047051415663,"sku":"TAK-TLK18100","price":3017.3,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/TLK18100_Mewlon-180C_1.jpg?v=1786911777","url":"https:\/\/ontariotelescope.com\/products\/takahashi-mewlon-180c-180mm-f-12-dall-kirkham-ota-with-dovetail-plate","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}