The best observation is achieved by combining an excellent optical tube with a performance close to the diffraction limit with an excellent eyepiece. This combination optimizes the resolution of the instrument over the entire field of view. The Takahashi TOE eyepieces were designed with this goal in mind. Whether on Takahashi telescopes or those of other prestigious brands, they allow the objectives of the various optical tubes to reach their full potential, especially in terms of resolution. They show that telescopes such as the TOA, TSA, FOA and FSQ or telescopes such as the Mewlon-CRS are not only photographic instruments, but also impressive tools for visual observation.
Takahashi TOE eyepieces are designed for observing the moon and planets at high magnification with optimal comfort. The TOA-130 telescope uses 4mm, 3.3mm and 2.5mm eyepieces to achieve magnifications of 250x, 300x and 400x, respectively. For the FSQ refractor at F/5, it is highly recommended to use an extender to switch to F/8 in combination with the ECG. The apparent field of view of the ECG is 52°, wider than the 40° of the old Hi-LE eyepiece, and the interpupillary distance is identical to that of other Takahashi eyepieces such as the LE-5 or LE-7.5, which makes planetary observation particularly comfortable.
Optical aberrations in eyepieces are theoretically difficult to assess. Therefore, Takahashi calculates the optical properties of the eyepieces and minimizes the aberrations, assuming that the eyepiece is a complete optical system mounted afokal to the focus of the TOA-130 refractor. From a wave-like point of view, the Strehl ratio does not fall below 98%, regardless of the wavelength under consideration (from 486 nm to 656 nm) and over the entire field. From a geometric point of view, the spot diagram shows that the resolution is well below the Dawes limit calculated for the TOA-130 lens. Finally, it should be noted that the remaining chromatic aberration is extremely low.
The optical design of the TOE eyepieces consists of 6 lenses divided into 4 groups. The Smyth lens of the first group and the main lens of the last group have been optimized to minimize spherical aberration, chromatic aberration, field curvature, and astigmatism. Ghosting and reflections have been reduced so that the moon and planets can be observed with high contrast. Each optical surface is treated with a full multi-layer broad-spectrum treatment, and an alternative treatment is applied to surfaces where the color balance needs to be corrected and contrast improved. Finally, all lens edges and inner metal surfaces are blackened to avoid scattered rays.