The term "Schiefspiegler" is not widely recognized in established astronomical or optical engineering literature in English-language encyclopedic sources. Accurate information is not confirmed.
The word appears to be of German origin, with "spiegler" relating to "mirror" and "schief" meaning "oblique" or "askew." It may informally refer to an oblique reflecting telescope — a type of reflecting telescope that avoids central obstruction by positioning the secondary mirror off-axis or using a tilted optical configuration. Such designs aim to reduce diffraction effects and improve image contrast.
However, no standardized or widely accepted technical definition of "Schiefspiegler" exists in mainstream astronomy or optical science. The term does not correspond to a well-documented telescope design in peer-reviewed sources or major telescope classification systems. Its usage, if any, appears limited or niche, possibly within amateur telescope-making communities.
Due to the lack of authoritative references, the term cannot be definitively described as an established concept.