| This short focal length Takahashi eyepiece uses a proprietary five-lens optical design to provide a high magnification capability with exceptional sharpness and contrast. The eyepiece uses an ED (Extra-low Dispersion) glass element for outstanding color correction. While it is a different design, this Takahashi is similar in its optical performance to a classical Abbe-type orthoscopic. It has the high contrast, low ghosting, flat field, and excellent edge to edge image sharpness for which orthos are famous – but has a 52° apparent field of view that far outstrips the 40-42° field more typical of a conventional ortho. The 5mm Takahashi makes an excellent lunar and planetary eyepiece with scopes of all optical types – fast focal ratio apochromatic refractors, Schmidt-Newtonian and Dobsonian reflectors, and more. Its high contrast and low ghosting also excel at splitting close binary star pairs and resolving globular clusters. It typically provides the maximum useful power with an f/10 Schmidt-Cassegrain. It generally provides excessively high powers with scope focal ratios longer than f/10 and is not recommended for scopes in this range, except for limited periods of lunar and planetary observing during exceptional seeing conditions. |
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