Planewave CDK20 F6.8 Optical Tube Assembly

Planewave CDK20 F6.8 Optical Tube Assembly

£44,880.00✓ 2 year warranty


Out of stock due 30-40 working days

About this product

Model:  planewave_cdk20_F68
Part Number:  1323220Q

The 20 "CDK astrograph from PlaneWave is a new, revolutionary telescope, which was specially designed to guarantee diffraction-limited imaging with large-format CCD cameras with an absolutely flat image field. In addition, the telescope is ideal for visual observation. It is with a modified Cassegrain system according to Dall-Kirkham with an additional corrector

Another key feature of the CDK 20 is its easy and uncomplicated collimation and centering of the optical system so that the observer can get the best out of the instrument.

The off-axis image quality surpasses that of most commercial optical designs, including that of the Ritchey-Chrétien. The RMS spot size in the outermost corner of the 35 mm image format is smaller than a single pixel in today's large format CCD cameras. The CDK20 is a half-meter telescope with a focal length of 3454mm that illuminates an image field of 52mm. It forms the link between the amateur and the public observatory. 

Price includes 1323520 Shipping and Storage Crate

Note: Photo also shows a GM4000HPS mount, TEC160, Pentax75 and CelestronED80. These are not included smiley

  • CDK 20 astrograph, 20 "(500 mm) with quartz glass optics
  • modified after Dall-Kirkham, with fully corrected image field
  • with 8 "temperature-compensated dovetail, 3,454 mm focal length (f / 6.8), 52 mm field of view
  • prepared for Delta T Heater (Hedrick focuser and EFA kit available separately)


  • Optical Design: Dall-Kirkham (CDK)
  • Aperture: 20"
  • Focal length: 3454mm
  • Focal Ratio: F6.8
  • Corrected Field of view: 52mm
  • Back Focus: 147mm behind the focusing unit
  • Obstruction: 39% (Diameter)
  • Mirror Type: Quartz Glass
  • Tube Weight: 54kg
  • Tube Length: 1194mm

CDK20 Features

Carbon Fibre Truss Design


Minimises thermal expansion which causes focus shift as temperature changes during an imaging session. Carbon fibre also reaches ambient temperatures quickly and is extremely lightweight and rigid to help ensure excellent imaging data is produced.


3D Printed Baffles

PlaneWave uses digital 3D printing technology to produce lightweight baffle tubes. 3D printers add successive layers of material to construct a baffle system with precision positioned internal stray light baffles to minimise vignetting and maximise image contrast. Quality baffling makes an incredible difference in overall image quality, so we ensured an optimal design was created for our telescopes.

Dovetail Expansion Joint


Allows for the difference in thermal expansion between carbon fibre and aluminium. The expansion joint allows the aluminium dovetail to expand and contract without stressing the carbon fibre lower truss. This results in images that are not distorted due to expansion, or contraction of the optical tube materials.


Delta-T Ready


For added dew prevention, the CDK20 is internally wired with polyimide film heater pads and temperature sensor, which is ready to be controlled with the Delta-T via PlaneWave Interface 3 software.


Cooling Fans


Three fans on the backplate of the optical tube pull air through the telescope and by the primary mirror. Three fans on the side of the optical tube also blow air across the primary to ensure a boundary layer of air does not distort images. These fans help the telescope reach thermal equilibrium quickly, further reducing any distortion in images due to temperature variations. The fans are controlled by a switch on the optical tube, or can be controlled by via PWI3 software if a PlaneWave Electronic Focus Accessory (EFA Kit) is purchased.


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