The CDK [Corrected Dall-Kirkham] telescope is based on a new optical design developed 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 end result is a telescope which is free from off-axis coma, off-axis astigmatism, and curvature of field, yielding a perfectly flat field all the way out to the edge of a 52mm image circle. This means pinpoint stars
from the center out to the corner of the field of view.
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 52 to 70mm image plane.
Optical Performance
At this point, we will show you two diagrams, to convince you about the high image quality of the CDK20. The first...