Zytra Tech. CDK17

This 17″ CDK is the first telescope that I designed and made. It is a fairly simple truss design (carbon fiber tubes) with an anodized aluminum structure. As opposed to the Dall-Kirkham, this Corrected DK has two corrector lenses located in the baffle assembly. Light is first reflected on the primary mirror, then reflected back toward the back of the telescope by the secondary mirror, then goes through both corrector lenses before going through the imaging train, in my composed of a large 3.6″ focuser, the SX Active Optics, my custom made OAG and finally my imaging camera a Moravian Instruments G3-11000.


  • Aperture: 431.8 mm (17″)
  • Focal Ratio: f/6.8
  • Focal Length: ~ 3,000 mm
  • Structure: CNC Aluminum (anodized)
  • Truss: Carbon Fiber tubes
  • Rear Cell Connection: M117x1 thread
  • Compatible with Moonlite Focusers (I am using their 3.6″ CXL)
  • 3x 60mm cooling fans with automatic temperature control
  • Weight: ~ 30 Kg (~ 65 lbs)

Build log:


  • Design: Started June 2012
  • Structure Fabrication: Started September 2012
  • Optics Shipped: October 2013
  • Optics Received: January 2014
  • Final Assembly: September 2014
  • Installed: September 2014

Story: I had always wanted to design and build my own telescope, an astrograph particularly. No experience in grinding and figuring a mirror did not help. So I searched the internet extensively and realized that the Ritchey Chretien design which is a common astrograph design was difficult to produce, making them more expensive than newtonian for example, especially in the range of 12-16″ which I was targeted.

I contacted Hubble Optics in June 2012 about their CDK optics. I did not find much information or reviews but after talking with Tong extensively, I decided to request their specifications so I could design a structure for their 17″ CDK optics. I was concerned about the corrective lenses which add some complexity to the structure but I was seduced by the specifications and the somewhat easier collimation and spacing requirements than of an RC. Their pricing was also much more affordable so I figured that down the road I would be able to afford it.

After about a month of design, I started machining some parts and later that very same year I had a ‘nice’ telescope structure with no optics. Roughly 18 months later the optics arrived, and another 6 months later the optics were finally installed.

Build thread (on the Cloudynights.com forums): 17″ CDK and Equatorial Mounting

The following link will direct you to all articles related to my 17″ CDK telescope.


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