{"product_id":"takahashi-toe-4mm-eyepiece","title":"Takahashi TOE 4mm Eyepiece","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe TOE 4 mm is built for high-magnification visual observing. Paired with a premium telescope, Takahashi designed the TOE range to deliver performance close to the diffraction limit across the entire field of view. The apparent field is 52° — similar to Takahashi's LE series — with 10 mm of eye relief.\u003c\/p\u003e\u003cp\u003eThe optical design uses six elements in four groups, chosen to minimise spherical aberration, chromatic aberration, field curvature and astigmatism together rather than trading one against another.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThis is a good match if you observe planets, the Moon or double stars and want a short-focal-length eyepiece that holds up under high power.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e4 mm focal length:\u003c\/strong\u003e high magnification on any telescope.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e52° apparent field:\u003c\/strong\u003e matched to Takahashi's LE series.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e10 mm eye relief:\u003c\/strong\u003e generous for this focal length.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e6 elements in 4 groups:\u003c\/strong\u003e controls spherical and chromatic aberration, field curvature and astigmatism.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eClose to the diffraction limit across the field:\u003c\/strong\u003e Takahashi's stated design target for the range on a premium telescope.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eSix elements in four groups is a substantial design for a 4 mm eyepiece, and the element count is what buys the correction. Four separate aberrations are being controlled at once here — spherical and chromatic error, which soften the image everywhere, and field curvature and astigmatism, which specifically degrade the outer field. Simpler high-power designs typically correct the centre and let the edges go, or hold the field and give up eye relief. Retaining 10 mm of eye relief at 4 mm focal length is the practical benefit: the eye sits at a workable distance rather than pressed against the lens, which matters over a long planetary session.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eHigh-magnification visual observing: planetary detail, lunar features, and splitting double stars.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eFits standard focusers and diagonals. Takahashi publishes this eyepiece as \u003cstrong\u003enot parfocal\u003c\/strong\u003e, so a touch of refocusing is needed when swapping eyepieces. The TOE line also includes 3.3 mm, 5.5 mm, 7.5 mm and 10 mm focal lengths, all of which we stock — tell us your telescope's focal length and we will suggest a set that spaces the magnifications sensibly.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eA visual eyepiece:\u003c\/strong\u003e designed for the eye rather than a sensor, with no application in a prime-focus imaging train.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eNot parfocal:\u003c\/strong\u003e refocusing is needed between TOE focal lengths.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eMagnification depends on your telescope:\u003c\/strong\u003e divide your focal length by 4. On a long instrument that is a lot of magnification, so it pairs well with a longer TOE for less steady nights.\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 the focuser or diagonal like any eyepiece, with a touch of refocusing when you swap.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat magnification will I get?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eYour telescope's focal length divided by 4. A 1000 mm telescope gives 250x.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is it best used for?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003ePlanets, the Moon, and double stars.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow does it compare with the 3.3mm?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eSame 52° field and 10 mm eye relief; the 3.3 mm gives more magnification and asks more of the seeing.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I use it for astrophotography?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eIt is a visual eyepiece with no application in a prime-focus imaging train.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eA six-element 4 mm eyepiece with a 52° field and 10 mm of eye relief — Takahashi's high-power option for planetary and lunar work.\u003c\/p\u003e","brand":"Takahashi","offers":[{"title":"Default Title","offer_id":54086046908527,"sku":"TAK-TKA00615","price":474.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/tka00615_2_5.jpg?v=1787329029","url":"https:\/\/ontariotelescope.com\/products\/takahashi-toe-4mm-eyepiece","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}