SKY-90 main features
Apochromatic objective with Fluorite doublet
The SKY-90, in spite of its short focal distance, is adapted to all the fields allowed by its aperture, thanks to its very wide chromatic correction and thanks to some subtle compromises : a light under-correction of the spherical aberration at prime focus, the Extender-Q/corrector 1.6x optional addition and an objective assembled on adjustable barrel. For more details, see Optical section.
Mechanics
In order to fulfill the pointed requirements of imaging, the SKY-90 does not make any concession on mechanics. It is equipped with a precise, tighted rack-and-pinion focuser as well as a device of blocking the focuser course. The focuser end offers a 50.8mm adapter which it is placed very in front of the focal plane, to allow a great combination of accessory assemblies, including with imagers equipped with large CCD sensors.
Retractable dewshield
The SKY-90 is of an exceptional compactness. Once the dewshield retracted, the length of the optical tube assembly is only of 480mm, except optional accessories placed at prime focus. A considerable asset for all those willing to have a transportable instrument for the imaging and for the observation. The tube weighs only 3,2 kg.
Visual and photo
Takahashi, as usual, proposes a vast range of accessories for all kind of uses, visual and photographic. For imaging use, the addition of the optional flattener is strongly recommended in order to optimize the performances of the refractor (see the System-charts heading).