{"product_id":"takahashi-ortho-extender-2x-barlow","title":"Takahashi Ortho Extender 2x Barlow","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe Ortho Extender 2x is Takahashi's 2x Ortho Barlow: a 130 g, 46 mm x 91 mm barlow lens with a 31.7 mm (1.25\") input barrel, designed to double focal length without adding aberration to an already well-corrected telescope. Unlike a fixed 2x Barlow, its actual magnification is a function of back focus — published by Takahashi as M = 2 + 0.0121 × b, where b is the distance in mm behind the Barlow. At zero back focus it is exactly 2.00x; add distance behind it, as a diagonal or T-mount train does, and the figure climbs from there.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThis is what you need if you observe or image the moon, planets or double stars and want to reach beyond your eyepiece set's shortest focal length — or add reach for a small-sensor camera — without introducing the aberration a lower-quality Barlow adds.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe magnification formula is the part worth understanding before you buy. Takahashi publishes three reference points: at 0 mm of back focus — an eyepiece inserted directly — magnification is exactly 2.00x. Behind a T-mount train (roughly 50 mm of back focus), it works out to about 2.61x. Behind a prism star diagonal, at 63.5 mm of back focus, it reaches 2.77x. The lens design — two elements in one group — is built to hold correction across that whole range rather than being optimized for one fixed spacing, and for visual use it is parfocal: swapping eyepieces at a given back focus does not require refocusing. On the camera side, the barrel is a 31.7 mm female sleeve with an M42 x 0.75 male T-thread built in, so it accepts a T-mount directly as well as a standard 1.25\" eyepiece or camera nosepiece.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigh-power lunar and planetary observation\u003c\/strong\u003e with your existing 1.25\" eyepieces, at roughly 2x their marked magnification.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSmall-sensor planetary and lunar imaging\u003c\/strong\u003e through the T-thread, where the extra reach concentrates detail on a small chip.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDouble star splitting\u003c\/strong\u003e at the higher power the 2x factor provides.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe barrel accepts standard 31.7 mm (1.25\") accessories on the input side. On the output side, the built-in M42 x 0.75 thread takes a T-mount directly, or a 1.25\" eyepiece for direct visual use. Because the actual magnification depends on what sits behind the Barlow — a diagonal, a T-mount adapter, or nothing at all — the figure to check is your own back focus, not a single quoted number. If you want your exact magnification worked out for your eyepiece, diagonal or camera train, send us the details and we will calculate it with you.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\u003cli\u003e\n\u003cstrong\u003eMagnification is not a single fixed number.\u003c\/strong\u003e It runs from 2.00x at zero back focus up to 2.77x behind a prism diagonal, per Takahashi's published formula. Check where your accessory sits in that range before assuming a flat 2x.\u003c\/li\u003e\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 drops into the eyepiece holder or camera train like any 1.25\" accessory, with no adjustment needed.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhy isn't the magnification always exactly 2x?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eBecause a Barlow's power depends on how far behind it the image forms. Takahashi publishes the relationship as M = 2 + 0.0121 × b: 2.00x with an eyepiece inserted directly, climbing to 2.77x with 63.5 mm of back focus behind a prism diagonal.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes it work for imaging as well as visual use?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eYes — the built-in M42 x 0.75 T-thread takes a camera directly, and the parfocal design means eyepiece and camera views stay in focus together at a given spacing.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat's it best used for?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eLunar and planetary work — visual or imaged — where extra reach on your existing eyepieces or a small sensor is the goal.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eIn short: a 130 g, parfocal 2x Barlow whose real magnification runs from 2.00x to 2.77x depending on what's behind it — tell us your eyepiece or camera train and we'll work out your number.\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/takahashi-2x-ortho-barlow-tka00598-magnification-chart.jpg?v=1786913723\" alt=\"Takahashi 2x Ortho Barlow magnification versus back focus chart, magnification equals 2 plus 0.0121 times back focus in millimeters\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e","brand":"Takahashi","offers":[{"title":"Default Title","offer_id":54047112560751,"sku":"TAK-TKA00830\/TKA00598","price":195.91,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/TKA00598_1.jpg?v=1786914045","url":"https:\/\/ontariotelescope.com\/products\/takahashi-ortho-extender-2x-barlow","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}