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The Cassegrain has a parabolic primary mirror and a hyperbolic secondary mirror, which reflects the light back down through a
hole in the primary. The Dall-Kirkham has an elliptic primary mirror and a spherical secondary mirror.
Combining these designs make this a compact optical system. On smaller telescopes, and camera lenses, the secondary is often mounted on an
optically flat, clear glass plate that closes the telescope tube. This support eliminates the "star-shaped" diffraction effects caused by a straight-vaned support spider. The closed tube stays clean, and the primary is protected, but at the cost of some loss of light-gathering power.
The Toscanoptics Cassegrain-DK makes use of the special properties of parabolic and hyperbolic reflectors. A concave parabolic reflector will reflect all incoming light rays parallel to its axis of symmetry to a single point, the focus. A convex hyperbolic reflector has two foci and will reflect all light rays directed at one of its two foci towards its other focus. The mirrors in this type of telescope are designed and positioned so that they share one focus and that the second focus of the hyperbolic mirror will be at the same point at which the image is to be observed - usually just outside the eyepiece.
Toscanoptics also provides the motorized secondary mirror for focusing on the focal plane without shift. This 'secondary' focuser is an original Toscano design that allows the secondary mirror to move in precise increments without any backlash. So it is a true "zero image shift" focuser!
It not only matters which telescope you buy but also where you buy it. Our additional services:
- We are a leading telescope dealer and know the devices we sell. Our customer service team will gladly help you after your purchase if you have problems with assembly or operation.
- We provide a copy of the 80-page Telescope ABC beginners handbook with every telescope.
