Kowa enjoys a spectacular reputation of enduring quality internationally, where there are large numbers of nature enthusiasts.
Kowa's 66mm series employ the great features of their world class flagship model, the TSN-821 M, in a smaller scope. Despite having a larger front element than two well-known 65mm scope competitors, the heaviest of the Kowa versions is still lighter than the lightest of their European brethren.
It is entirely a matter of personal preference best determined by experience, but many feel that straight scopes offer a more intuitive way to locate your subject quickly. They're usually a bit lighter than their angled counterparts, and almost always less expensive as well.
The TSN-664 uses an element of ED (extra-low dispersion) glass in its construction, which greatly minimizes chromatic aberration. Most spotting scopes are essentially refractor telescopes built for harsh abuse, with permanently included prisms to render the terrestrial world upright and laterally correct. For all their contrast and resolution, refractor telescopes did fall out of favor with astronomers for their false coloring at the image periphery (chromatic aberration).
This problem becomes more prevalent the larger and longer the refractor is and is easily seen in astronomy-but much harder to detect in birding, for example. But if you view a bird in front of a bright sky background with a normal scope, you'll see some fringing on the edge of the subject where it meets the sky in your view. This may appear as a blue or purple hazy line. Glass with ED elements greatly reduce this effect.
TSN-664 2.6"/66mm Spotting Scope with Fluorite (Requires Eyepiece)
Front & Rear Caps
Limited Lifetime Warranty