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With the Wolterscope 150 (170/200) you have purchased an optical instrument of high quality of the Schiefspiegler type. The Schiefspiegler design has been developed by Anton Kutter in Germany [see references]. Mr. Kutter tried to avoid the central obstruction caused by the secondary mirror in a Cassegrain type telescope. The obstruction by the secondary mirror results in some light loss and which is more seriously - it reduces the image contrast. Therefore Mr. Kutter uses a tilted primary mirror which reflects the light to a position outside of the light path. Another tilted mirror (secondary mirror) is located there and reflects the light to the final focus.
The Schiefspiegler avoids the central obstruction and because it only uses reflections no color errors will be present. Therefore the image quality of a Schiefspiegler is comparable to that of high quality refractors of the same size. This has been proven practically by many amateurs and is documented by photographs of the moon and planets of high quality.
The new Multi-Schiefspiegler is based on this concept of Mr. Kutter and developed it further [see references].
This design adds a third mirror to the optics and one of the mirrors is used twice. Therefore a total of 4 reflections is obtained. The sequence of reflections (1-4) is displayed in the following image. Finally, after the 4. reflection the image is formed at the focal plane, which is located behind the primary mirror. The geometry of this design is therefore similar to that of a refractor and allows a convienient observing position. The new optical principle of the Multi-Schiefspiegler is protected by patents from commercial use [see references].
Multi-Schiefspiegler-theory
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Ray-tracing shows, that this optical design yields favourable optical properties. The image errors induced by the tilt of the primary are perfectly compensated by the additional mirrors. The design allows larger f-ratios than the classical Schiefspiegler, it is more compact and even apertures up to 1m are possible theoretically.
The center of gravity of the tube was located not far away from the focuser, so the observer has to change his position only by a small amount, which is very comfortable.
The Multi-Schiefspiegler can also be used for astronomical photography. The image is tilted by a maximum of 1.5° with respect to the optical axis and this can be neglected in most cases. This value is far less than that of other Schiefspiegler designs. The curvature of the image plane is very small and not detectable. The photographic field of view is restricted by the size of the secondary mirror, which defines the unvignetted field of view.
This telescope is able to show all types of observable astronomical objects, because of its medium light power (f-ratio). No special and costly eyepieces are necessary to obtain a certain magnification. The optics yields an image quality which is only limited by the diffraction at the entrance aperture. The remaining image errors of the optical system are far below diffraction limit and therefore not detectable. Only mirrors of high surface quality and of highest reflectivity are used to produce this telescopes to ensure the highest optical performance.
Due to the compactness of the design and its limited tube weight, this telescope can be easily carried to favourable observing places.
More details about the construction and theory of the Multi-Schiefspiegler are found on the following pages:
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