I didnt believe that Takahashi could do much to improve upon their already excellent FS series of refractors, but this TSA-102S set new standards for APO performance in the 4-inch class. The scope displays absolutely no false color, spherical aberration, astigmatism, or any other optical deficiency. The star test reveals textbook perfection and an ultra-smooth optical figure. Stellar images show a hard, sharp Airy disk and delicate first diffraction ring: virtually ALL of the light is going exactly where it should as in the theoretical model of perfection. Close double stars of traditional difficulty are handled with ease, including Eta Geminorum and even Sirius. Planetary detail is rich, color-pure, and wonderfully sharp. Contrast is exceptional. Lunar features are seen in stark, razor-sharp detail with no trace of spurious color or image breakdown even at absurdly high magnifications. Because of its optical quality, it seems to cut through poor seeing conditions and still deliver satisfying images while lesser scopes are incapacitated. Though limited by aperture, the TSA also provides fine deep-sky vistas with its excellent light transmission and effective baffling of stray light. At just 11 pounds, the scope is quite portable and can be mounted on a CG5 equatorial or Unistar alt-az mount with good results in stability and damping time. The TSAs rack & pinion focuser is buttery smooth and permits a very nice snap to focus, though some observers might want to upgrade to a dual-speed retro-fit. The f/8 focal ratio is rather long - making for great visual observing, but Tak does offer an optional focal reducer for those who are into ccd imaging and/or photography. After having owned nearly 20 ED and APO refractors over the years and having looked through many more, I can say that none have topped the performance of this TSA-102S, and most have fallen well short of its optical quality.

Four inch apos dont get any better than this. Outstanding optics, rugged construction. I am using it for imaging with ST2000xcm and getting excellent results.