Gregorian Telescope past and future collide

The Gregorian telescope was first designed by James Gregory (1638-1675). It uses a paraboloidal primary mirror and a concave ellipsoidal secondary. Collecting light and bringing it to a focus is done by the primary, and the secondary reflects the beam, through a hole in the center of the primary and out the bottom of the instrument. The Gregorian requires a long tube and eliminates chromatic and spherical aberration.

On March 30th 2004 the Compact Gregorian Telescope was invented by Vladimir Draganov. The primary mirror is designed with a concentric "double-curved" geometry. This is done by flipping the secondary mirror over a folding mirror in the middle of the optical path between the primary and secondary mirrors. Now this compact can be as short as 1/7th the focal length of the systems.

The "double curved" mirror surface of the Compact Gregorian Telescope is the result of new techniques for producing diamond-turned mirrors. Uses for this instrument are free space communications, night visions, astronomy, laser radar, remote sensing, military, and microscopy.