NAKOH 60GT Astrograph Triplet APO
A compact astrograph defined by high quality and exquisite design.
Its triplet lens design masterfully utilizes one piece of Japan-made SD glass and one piece of ED glass to minimize chromatic aberrations, delivering consistently sharp, high-definition results. Enjoy flat, clear, and stunning stellar views that are maintained from the image center all the way to the 44mm full-frame edge.
The optical performance of the NAKOH 60GT has been rigorously tested using the internationally recognized ZYGO interferometer, with quantitative data demonstrating top-tier excellence.
The test report reveals a Strehl ratio as high as 0.976, an RMS value as low as 0.026λ (surpassing λ/38), and a PV value of 0.168λ. These figures not only far exceed the demanding "diffraction-limited" standard (Strehl ratio > 0.8) but also indicate that its imaging quality is virtually unconstrained by mirror precision, allowing celestial details to be concentrated into an exceptionally sharp focus.
Mechanical Features
Dual-speed metal rack-and-pinion focuser with a 2.5-inch interface, 32mm focusing travel, and high-precision engraved scales.
Compatible with most commercially available electronic focusers. The focuser side features a finder base (M4 threaded hole) for additional astronomical accessories.
The fine adjustment knob includes a protective cap to prevent damage.
Equipped with a 360° high-precision rotator featuring engraved scales, a knurled locking screw allows for secure fixation of the rotation angle.
230mm length Vixen-style dovetail plate, equipped with standard threaded holes.
Full metal tube rings with a tilted design for superior fixation. Enlarged thumb locking screws enable easy operation.
Full-metal, detachable handle with a streamlined design for a comfortable grip.
Design Features
* The NAKOH 60GT is a triplet APO astrograph, utilizing one piece of SD glass and one piece of ED glass.
Optical Path Diagram
It fully leverages the anomalous dispersion characteristics of both SD and ED glass to significantly reduce differences in the refractive index across various wavelengths. This effectively suppresses chromatic aberration (particularly purple and green fringing) and enhances image sharpness.
* The imaging quality of the optical system can be evaluated by analyzing the distribution of star points in the image.
60GT+1.0× Flattener Spot Diagram
60GT + 0.65× Reducer Spot Diagram
The horizontal axis represents the distance of the star point from the image center, while the vertical axis represents the RMS radius of the star point.
The NAKOH 60GT achieves a central star RMS radius of approximately 2 micrometers, and less than 2.5 micrometers at the edge of the 44mm image circle.
The stars are sharp and rounded, demonstrating excellent performance across the full frame.
60GT Longitudinal chromatic aberration Curve
The longitudinal chromatic aberration graph uses wavelength (nm) as the horizontal axis and focal shift (μm) as the vertical axis to display differences in the focusing positions of various wavelengths along the optical axis. The NAKOH 60GT exhibits low shift, a gentle curve across the entire wavelength range, and well-aligned curves at key wavelengths, reflecting its excellent chromatic aberration control.
The relative illumination uses the field radius as the horizontal axis and relative brightness percentage as the vertical axis to illustrate the attenuation of light from the center to the edge of the field of view. Even at the extreme edges of the full frame, the 60GT maintains high brightness, a smoothly declining curve, and consistency across multiple wavelengths, effectively minimizing vignetting.
Ronchi test
In focus
Out of focus
The Ronchi test quantitatively evaluates the surface figure accuracy and optical axis collimation of the objective lens by analyzing shadow patterns. The 60GT demonstrates exceptional performance: both in and out of focus, the shadow variations transition evenly and smoothly, forming straight, symmetrical lines.
This conforms to the criteria of an excellent optical system, indicating that the 60GT possesses precise parabolic surface figures and optimal optical alignment.
Samples
Sample1:NGC6960
〈Objects〉IC：NGC6960 photographed by：Zhang Yuhang
equipments：NAKOH 60GT + Specific 1.0× Flattener Camera: ZWO ASI6200MM
Sample2:M45
〈Objects〉IC：M45 photographed by：Qiang
equipments：NAKOH 60GT + Specific 0.65× Reducer Camera: ZWO ASI2600MC
Technical Specification
| Aperture/Focal Length /Focal Ratio |
60mm / 360mm / F6 |
| Objective Lens |
triplet APO (incl. 1× SD Glass [made in Japan], 1× ED Glass) |
| Image Circle |
φ44mm (with Reducer/Flattener)
|
| Resolving Power/Limiting Magnitude |
1.93 arc seconds/10.66
|
| Light Gathering Power |
73x unaided eyes
|
| Tube Length |
270mm |
| Weight |
≈2.94kg |
| Rear-end Interface |
1.25-inch / 2-inch
|
| Standard Accessories |
60GT，Handle，Tube Ring，Dovetail Plate，1.25-inch Adapter，2-inch Adapter，Instruction Manual ，Warranty Card
|
Product Size Diagram & Connection Diagram
【Product Size Diagram】
【Connection Diagram】
* Observation Mode
* Imaging Mode
In the box
-
Optical Tube Assembly (OTA)
- Handle
- Tube Ring
- Vixen-style Dovetail Plate
- 1.25-inch Eyepiece Adapter/ 2-inch Eyepiece Adapter
- UserManual/ WarrantyCard
Warranty & Manual
NAKOH Warranty
