The CDK telescope is a brand new optical design invented by Dave
Rowe.  The goal of the design is to make an affordable astrographic
telescope with a large enough imaging plane to take advantage of the
large format CCD cameras of today.  Most telescope images degrade as
you move off-axis from either coma, off-axis astigmatism, or field
curvature.  The CDK design suffers from none of these problems.  The
CDK is coma free, has no off-axis astigmatism, and has a flat field. 
The design is a simple and elegant solution to the problems posed
above.  The CDK consists of three components:  an ellipsoidal primary
mirror, a spherical secondary mirror and a lens group.  All these
components are optimized to work in concert in order to create superb
pinpoint stars across the entire 42mm image plane.