The history of the telescope makes for interesting reading. During the development of the telescope, carmit practical experiments with reflectors had already begun in 1639, but it was not until 1663 that they gained any prominence.
The Gregorian Telescope
In that year a Scottish mathematician, James Gregory, at the age of 24, published a treatise entitled Optica Promota. In this he gave a description of a compound reflecting telescope employing two concave specula (metal mirrors). The larger one was to be perforated, and to have a paraboloidal surface; the smaller was to be ellipsoidal. High magnification could be had with this instrument, the second reflection amplifying the focal length of the primary in the ratio of fs to Fs.