To design his new range of eyepieces, Takahashi simulated the combination of numerous eyepiece optical formulas at the focus of aberration-free instruments, such as the TOA apochromatic refractor and the Mewlon CRS telescope. The best possible combination was obtained using the Plössl formula redesigned by Takahashi.
Plössl eyepieces are often underestimated because they are seen as cheap, low-quality and mass-produced eyepieces. Takahashi has decided to restore a classic optical design to its former glory, but one that offers a host of advantages, provided it is designed and manufactured with the utmost care. To achieve this, the prestigious Japanese manufacturer has used very low chromatic dispersion glasses and ensured that the exact optical characteristics of the lens with which the eyepiece is associated are restored to the eye. At the center of the field, chromatic aberration is reduced by half compared to the Abbe series and by two-thirds compared to the LE series.
For this type of eyepiece, which has no Smyth lens, the Petzval sum cannot be reduced to zero, so a flat field cannot be fully achieved. Despite this, it can still be optimized. Astigmatism and field curvature of TPL eyepieces are perfectly controlled to minimize distortion of stars at the edge of the field. Image quality is excellent from the optical axis to halfway across the field of view. And even if the stars tend to widen slightly at the edges, the image remains very good visually; the observer naturally observing more the center of the image than its periphery. Because of this design, the field of TPL eyepieces will be flattened when combined with a quality short Barlow lens.
All lenses are multi-coated, with transmission greater than 99% over the entire visible spectrum. Contrast is maximized thanks to precise machining of mechanical elements and baffles. The eye relief is around 70% of the eyepiece focal length, and a retractable rubber bonnet allows ideal placement, whether you wear prescription glasses or not.
The apparent field of view is 48°. All TPL eyepieces have the same focal lengths as other Takahashi eyepieces (old LE or Abbe) with a 1.25" (31.75 mm) barrel.
