{"product_id":"takahashi-starbase-ke-25mm-kellner-eyepiece","title":"Takahashi Starbase KE-25mm Kellner Eyepiece","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe Starbase KE-25mm is a 25mm Kellner eyepiece from Takahashi's Starbase accessory line, built around the same 2-groups, 3-element optical layout as the KE-20mm. It delivers a 45° apparent field of view and 18mm of eye relief, and weighs 77g — the longest focal length, and so the lowest power and widest exit pupil, in the Starbase Kellner pairing.\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 the lowest-power, widest-view eyepiece in your case — for locating targets, scanning the Milky Way, or getting a bright, easy view before moving to a shorter focal length for detail.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eKellner optical design:\u003c\/strong\u003e 2 groups, 3 elements, simple and well-corrected at the center of the field.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e45° apparent field of view:\u003c\/strong\u003e a wide window at 25mm focal length.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e18mm eye relief:\u003c\/strong\u003e generous, comfortable for eyeglass wearers.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e77g weight:\u003c\/strong\u003e matches the KE-20mm, so the pair balances the same way in a focuser.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe Kellner layout — a plano-convex field lens paired with a cemented achromatic eye lens — keeps the design simple while holding correction at the center of the field, which is where a low-power, wide-view eyepiece like this one is used most. At 25mm, this is the longer of the two Starbase Kellner focal lengths, producing the largest exit pupil and lowest magnification in the pairing.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eOn a Takahashi FS-60CB (355mm, f\/5.9) the KE-25mm gives about 14x, a very wide, bright view suited to large star fields and the Milky Way. On a TSA-120 (900mm, f\/7.5) the same eyepiece yields roughly 36x — useful as a locating eyepiece before switching to higher power. Divide any Takahashi tube's focal length by 25mm for the magnification on your own setup.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eMost of the Starbase and Takahashi eyepiece lines use the 1.25” (31.7mm) barrel standard, which fits every current Takahashi focuser, star diagonal, and 2″-to-1.25” adapter.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eNot parfocal with the rest of the range:\u003c\/strong\u003e expect to refocus when you swap eyepieces.\u003c\/p\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 any 1.25” focuser or diagonal and is ready to use immediately.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is it best used for?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eLow-power, wide-field visual observing — locating targets, scanning star fields, and framing before you switch to a shorter focal length.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow does it compare to the KE-20mm?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eSame Kellner design and weight; the KE-25mm's longer focal length gives a lower magnification and larger exit pupil on the same telescope, useful as the wide end of a two-eyepiece kit.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat telescopes does it fit?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eAny Takahashi refractor or reflector with a standard 1.25” focuser or diagonal.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eA 25mm Kellner eyepiece with a 45° field and 18mm of eye relief — the widest, lowest-power option in the Starbase Kellner pairing. If you're building out a full eyepiece set and want help matching focal lengths to your telescope, send us your setup and we'll work it out with you.\u003c\/p\u003e","brand":"Takahashi","offers":[{"title":"Default Title","offer_id":54047075008623,"sku":"TAK-SBP08080","price":72.93,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/sbp08080_3.jpg?v=1786912734","url":"https:\/\/ontariotelescope.com\/products\/takahashi-starbase-ke-25mm-kellner-eyepiece","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}