PlaneWave - 12.5" CDK Corrected Dall-Kirkham Carbon Fiber Telescope

PlaneWave 12.5" CDK 

 

The new CDK optical design is the innovative solution for unsurpassed astroimaging quality at an affordable price. The purpose of the design is to provide a telescope that will excel at imaging with large format CCD cameras while remaining superb for visual use. The CDK design far exceeds the off-axis performance of most commercial telescope designs including the Ritchey-Chretien design. The RMS spot sizes at the edge of a 52mm diameter image circle yield are 12 microns, about the size of a pixel of most CCD cameras.

This no-compromise design is unique in making the optical alignment very forgiving and collimation very easy. This guarantees the user will be sure to get the best performance out of the telescope possible. The end result at the image plane of the CDK design is no off-axis coma, no off-axis astigmatism, perfectly flat field (no off-axis defocus), all the way out to a 52mm image circle. All this means, the stars will be pinpoints from the center of the field of view out to the corner of the field of view.

Features and Specifications

System

• Aperture 12.5"
• Focal Length 2541 mm
• Focal ratio f/8
• Central Obstruction 39%
• Back Focus 10.445" from focuser mounting surface, 7.2" from racked in focuser
• Weight 46 lbs
• OTA Length 31" 
• Optical Tube Carbon Fiber
• Optical Performance Vignetting Plot - Spot and Diffraction Diagrams
• Overall Dimensions Dimensions PDF

Primary Mirror

• Diameter 13"
• Aperture 12.5"
• Focal ratio f/8
• Mounting Laser Collimated and Permanentely Fixed 
• Material Precision Annealed Pyrex
• Shape Prolate Ellipsoid
• Coating Enhanced Aluminum - 96%

Secondary Mirror

• Diameter 4.65"
• Material Precision Annealed Pyrex
• Shape Spherical
• Coating Enhanced Aluminum - 96%

Lens Group

• Diameter 70mm
• Number of lenses 2
• Coating Broadband AR Coatings (less than .5% from 400 to 700nm)
• Standard Features

Carbon Fiber Tube Design Minimizes thermal expansion which causes focus shift with changes in temperature

Dovetail expansion joint Allows for the difference in thermal expansion between carbon fiber and aluminum. The expansion joint allows the aluminum dovetail expand and contract without stressing the carbon fiber lower truss

 

 

 

 

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.