Optical & Design Features

The NAKOH 60GT is a triplet APO astrograph using one SD glass element and one ED glass element to achieve superior chromatic correction.

By 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.

Spot Diagram Performance

The 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.

The 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.