{"title":"NAKOH Triplet Refractors","description":null,"products":[{"product_id":"nakoh-60gt-60mm-f6-triplet-apo-astrograph","title":"NAKOH 60GT 60mm f\/6 Triplet APO Astrograph","description":"\u003csection class=\"product-intro\"\u003e\n\u003cp class=\"txt\"\u003eA compact astrograph defined by high quality and exquisite design. The NAKOH 60GT features a triplet APO optical system incorporating one Japan-made SD glass element and one ED glass element to minimise chromatic aberration. For a corrected 44mm full-frame imaging field, use the separately sold matching 1.0× field flattener or 0.65× reducer. Neither corrector is included with the telescope.\u003c\/p\u003e\n\u003cp class=\"txt\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1766372823130753.jpg?v=1772012357\" alt=\"Nakoh 60GT 0.65× Reducer attached  on a white background\"\u003e\u003c\/p\u003e\n\u003cp class=\"txt\"\u003e\u003cem\u003eNAKOH is a Japanese optical manufacturer recently expanding into triplet APO astrographs with the launch of the 60GT series.\u003c\/em\u003e\u003cbr\u003e\u003cem\u003eFounded to bring high-precision astronomy optics to advanced amateurs and astroimagers, NAKOH combines Japanese engineering with modern design.\u003c\/em\u003e\u003c\/p\u003e\n\u003c\/section\u003e\n\u003csection class=\"product-specifications con3 top_about_figure_img\"\u003e\n\u003ch2\u003e\n Specifications \n\u003c\/h2\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eAperture \/ Focal Length \/ Focal Ratio\u003c\/td\u003e\n\u003ctd\u003e60mm \/ 360mm \/ f\/6\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eObjective Lens\u003c\/td\u003e\n\u003ctd\u003eTriplet APO (1× SD glass [Japan], 1× ED glass)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eImage Circle\u003c\/td\u003e\n\u003ctd\u003eØ44mm (with Reducer \/ Flattener)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eResolving Power \/ Limiting Magnitude\u003c\/td\u003e\n\u003ctd\u003e1.93 arcsec \/ 10.66\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLight Gathering Power\u003c\/td\u003e\n\u003ctd\u003e73× unaided eye\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTube Length\u003c\/td\u003e\n\u003ctd\u003e270mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e≈ 2.94kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRear Interface\u003c\/td\u003e\n\u003ctd\u003e1.25″ \/ 2″\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eStandard Accessories\u003c\/td\u003e\n\u003ctd\u003e60GT OTA, Handle, Tube Rings, Dovetail Plate, 1.25″ Adapter, 2″ Adapter, Instruction Manual, Warranty Card\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/section\u003e\n\u003csection class=\"optical-design con4 top_about_figure_img\"\u003e\n\u003ch2\u003e\n Optical \u0026amp; Design Features \n\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003e The NAKOH 60GT is a triplet APO astrograph using one SD glass element and one ED glass element to achieve superior chromatic correction. \u003c\/strong\u003e\u003c\/p\u003e\n\u003cfigure\u003e\n\u003cfigcaption class=\"pkg-text\"\u003eOptical Path Diagram\u003c\/figcaption\u003e\n\u003cimg alt=\"Nakoh 60GT optical path diagram showing light ray correction\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1768801415213511.jpg?v=1772008613\" loading=\"lazy\"\u003e\u003c\/figure\u003e\n\u003cp\u003eBy fully utilising the anomalous dispersion properties of SD and ED glass, the 60GT significantly reduces refractive index differences across wavelengths. This effectively suppresses chromatic aberration (especially purple and green fringing) while enhancing image sharpness and contrast.\u003c\/p\u003e\n\u003ch3\u003eSpot Diagram Performance\u003c\/h3\u003e\n\u003cdiv class=\"grid-2\"\u003e\n\u003cfigure\u003e\n\u003cfigcaption class=\"pkg-text\"\u003e60GT + 1.0× Flattener\u003c\/figcaption\u003e\n\u003cimg alt=\"Nakoh 60GT spot diagram with 1.0x flattener\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764837271206689.jpg?v=1772008613\" loading=\"lazy\"\u003e\u003c\/figure\u003e\n\u003cfigure\u003e\n\u003cfigcaption class=\"pkg-text\"\u003e60GT + 0.65× Reducer\u003c\/figcaption\u003e\n\u003cimg alt=\"Nakoh 60GT spot diagram with 0.65x reducer\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764837282156559.jpg?v=1772008613\" loading=\"lazy\"\u003e\u003c\/figure\u003e\n\u003c\/div\u003e\n\u003cp class=\"pkg-text\"\u003eThe horizontal axis represents the distance from the image centre, while the vertical axis represents the RMS radius of the star point. The 60GT achieves a central RMS radius of approximately 2μm and less than 2.5μm at the edge of the 44mm image circle, producing sharp, round stars across the full frame.\u003c\/p\u003e\n\u003cfigure\u003e\n\u003cfigcaption class=\"pkg-text\"\u003eLongitudinal Chromatic Aberration Curve\u003c\/figcaption\u003e\n\u003cimg alt=\"Nakoh 60GT longitudinal chromatic aberration curve\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764311738838998.jpg?v=1772008613\" loading=\"lazy\"\u003e\u003c\/figure\u003e\n\u003cp class=\"pkg-text\"\u003eThe longitudinal chromatic aberration graph plots wavelength against focal shift, illustrating the excellent colour correction of the optical system. The gentle, well-aligned curves indicate minimal focus shift across the visible spectrum.\u003c\/p\u003e\n\u003c\/section\u003e\n\u003csection class=\"illumination-performance\"\u003e\n\u003ch2\u003eIllumination \u0026amp; Vignetting Control\u003c\/h2\u003e\n\u003cdiv class=\"grid-2\"\u003e\n\u003cfigure\u003e\u003cimg alt=\"Relative illumination curve for Nakoh 60GT\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764837318113610.jpg?v=1772008612\" loading=\"lazy\"\u003e\u003c\/figure\u003e\n\u003cfigure\u003e\u003cimg alt=\"Relative illumination across full-frame field for Nakoh 60GT\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764837336155720.jpg?v=1772008613\" loading=\"lazy\"\u003e\u003c\/figure\u003e\n\u003c\/div\u003e\n\u003cp\u003eRelative illumination curves demonstrate high brightness retention from the centre to the extreme edges of the full-frame field. The smooth decline and wavelength consistency indicate excellent vignetting control.\u003c\/p\u003e\n\u003c\/section\u003e\n\u003csection class=\"optical-testing\"\u003e\n\u003ch2\u003eOptical Testing \u0026amp; Quality Control\u003c\/h2\u003e\n\u003cfigure\u003e\u003cimg alt=\"ZYGO interferometer test results for Nakoh 60GT\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764312604192493.jpg?v=1772008613\" loading=\"lazy\"\u003e\u003c\/figure\u003e\n\u003cp\u003eThe optical performance of the NAKOH 60GT has been rigorously verified using a ZYGO interferometer. Test results show a Strehl ratio up to 0.976, an RMS value of 0.026λ (better than λ\/38), and a PV value of 0.168λ—far exceeding the diffraction-limited standard.\u003c\/p\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"center\" colspan=\"2\"\u003e\u003cstrong\u003eRonchi Test\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"center\"\u003e\n\u003cp class=\"pkg-text\"\u003eIn Focus\u003c\/p\u003e\n\u003cimg alt=\"Nakoh 60GT Ronchi test in focus\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764313145695774.jpg?v=1772008611\" loading=\"lazy\"\u003e\n\u003c\/td\u003e\n\u003ctd align=\"center\"\u003e\n\u003cp class=\"pkg-text\"\u003eOut of Focus\u003c\/p\u003e\n\u003cimg alt=\"Nakoh 60GT Ronchi test out of focus\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764313126875470.jpg?v=1772008611\" loading=\"lazy\"\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp class=\"pkg-text\"\u003eThe Ronchi test results show smooth, symmetrical line transitions both in and out of focus, confirming excellent surface accuracy and precise optical alignment.\u003c\/p\u003e\n\u003c\/section\u003e\n\u003csection class=\"image-samples con5 top_about_figure_img\"\u003e\n\u003ch2\u003eAstrophotography Samples\u003c\/h2\u003e\n\u003cfigure\u003e\n\u003cfigcaption class=\"pkg-text\"\u003eNGC 6960 (Veil Nebula) — ZWO ASI6200MM + 1.0× Flattener\u003c\/figcaption\u003e\n\u003cimg alt=\"Veil Nebula captured with Nakoh 60GT\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764318293214149.jpg?v=1772008615\" loading=\"lazy\"\u003e\u003c\/figure\u003e\n\u003cfigure\u003e\n\u003cfigcaption class=\"pkg-text\"\u003eM45 (Pleiades) — ZWO ASI2600MC + 0.65× Reducer\u003c\/figcaption\u003e\n\u003cimg alt=\"Pleiades star cluster captured with Nakoh 60GT\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764313835676363.jpg?v=1772008614\" loading=\"lazy\"\u003e\u003c\/figure\u003e\n\u003c\/section\u003e\n\u003csection class=\"mechanical-features\"\u003e\n\u003ch2\u003eMechanical Features\u003c\/h2\u003e\n\u003cfigure\u003e\u003cimg alt=\"Nakoh 60GT focuser assembly\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1766121997126530.jpg?v=1772008614\" loading=\"lazy\"\u003e\n\u003cfigcaption class=\"pkg-text\"\u003eDual-speed 2.5″ rack-and-pinion focuser with 32mm travel and engraved scale. Compatible with most electronic focusers.\u003c\/figcaption\u003e\n\u003c\/figure\u003e\n\u003cfigure\u003e\u003cimg alt=\"Nakoh 60GT Vixen-style dovetail plate\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764314254212398.jpg?v=1772008613\" loading=\"lazy\"\u003e\n\u003cfigcaption class=\"pkg-text\"\u003e230mm Vixen-style dovetail plate with standard threaded mounting holes.\u003c\/figcaption\u003e\n\u003c\/figure\u003e\n\u003c\/section\u003e","brand":"Nakoh","offers":[{"title":"Default Title","offer_id":55474925142392,"sku":"60GT","price":899.0,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0523\/1650\/4241\/files\/1764227275144468.jpg?v=1782290532"}],"url":"https:\/\/www.darkclearskies.co.uk\/collections\/nakoh-triplet-refractors.oembed","provider":"Dark Clear Skies ","version":"1.0","type":"link"}