Planewave - CDK400 Observatory System

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The Planewave CDK400 includes a Planewave CDK17 telescope and the L500 Direct Drive mount.  Designed for affordability and high demand applications, this is a high precision observatory system.  

The CDK17 features a truss tube design, 3 built in cooling fans and fused silica optical glass for maximized temperature stability. 

Prewired to accept Delta-T. 

The L500 direct drive mount can be configured in either AZ or EQ, and with no gears the L500 exhibits zero backlash and no periodic error.

High resolution encoders provide feedback to counteract gusts of wind and further enhance mount precision. 

If you choose to place an order for this item, you will be contacted for crating and shipping fee information and options.  To receive a quote contact us at [email protected]

Planewave - CDK400 Observatory System

Built for exceptional optical and tracking performance, and, designed for astrophotography or research, the CDK400 observatory package includes a Planewave CDK17 and an L500 mount.  Building on a legacy of high performance 1 meter telescopes, Planewave has drawn from that same advanced optical system and precision direct drive mount to meet the demands of research and educational observatories.  The CDK400 observatory system was also designed to be an affordable observatory solution. 

The PlaneWave Instruments CDK17 is a 17 inch (0.43 m) f/6.8 Corrected Dall-Kirkham Astrograph telescope. The CDK17 has a dual carbon-fiber truss design, with 3 cooling fans ejecting air from the back of the telescope, and 4 fans blowing across the boundary layer of the mirror’s surface. The CDK17 covers a 70 mm field of view without any field curvature, off-axis coma, or astigmatism. The instrument weight is 94 lbs (43 kg) and comes standard with a backplate retaining ring ready to accept the focuser of your choice.

CDK400 Features

CDK17 Optical Tube:

  • f/6.8 and 2939mm focal length
  • No coma, no off-axis astigmatism, and no field curvature.
  • Pinpoint stars across a 70mm image circle.
  • Rock solid fused silica mirrors with low thermal expansion.
  • Carbon fiber optical tube assembly for rigidity and fast cooling.
  • Simple secondary mirror collimation thanks to the fixed primary mirror.
  • Pre-wired for Delta-T, and equipment with a polyimide film heater pads and temperature sensor.  DeltaT sold separately. 
  • 3 cooling fans at the rear of the primary and 3 cooling fans at the side of the telescope body, allow the system to reach thermal equilibrium quickly. 
  • Dovetail expansion joint provides a buffer between the expansion rate of the carbon fiber trusses and the aluminum dovetail for additional thermal stability. 
  • 3D printed baffles minimize stray light and vignetting, while maximizing contrast. 

Planewave Fused Silica Mirrors

With a coefficient of thermal expansion 6 times lower than Borosilicate Pyrex glass, fused silica optical glass is exponentially more stable as temperatures change.  For long observing or imaging sessions, this added stability reduces the need to adjust focus.  

3D Printed Baffles

Using 3D printing technology, Planewave is able to produce a lightweight successive layers with highly precise positioning to minimize stray light and vignetting while maximizing contrast. 

Dovetail Expansion Joint

To provide additional thermal expansion stability, the CDK24 is equipped with an expansion joint to account for the different expansion rates of the carbon fiber trusses and the aluminum dovetail.

Cooling Fans

Three rear cooling fans pull air through the optical tube near the primary mirror, and three additional fans blow air across the primary from the side of the telescope body.   This combination of fans and open truss design allow the CDK24 to reach thermal equilibrium quickly.   The fans are controlled by a manual switch on the optical tube or can be controlled with PWI3 software when the Planewave EFA kit is added. 

CDK vs. RC Optical Design

Ritchey Chretien optical design, though highly successful in eliminating many typical optical problems naturally found in preceding designs, does not correct off-axis astigmatism and field curvature.  While these issues can be corrected with the addition of correctors and flatteners as accessories to the telescope, David Rowe developed a new Corrected Dall Kirkham design that effectively incorporates these correctors into the optics. By utilizing an ellipsoid primary mirror, a spherical secondary mirror and a lens specifically configured doublet lens group, coma, off-axis astigmatism and field curvature are eliminated.  

L500 Mount

The Planewave L500 combines versatility, simplicity and affordability by combining all the technology of our Observatory class telescopes into a compact stand-alone mount. In its Alt/Az configuration, it is considerably more compact than its equatorial counterpart, allowing a larger telescope to fit in a smaller enclosure. The mass it takes to make a rigid alt/az mount is substantially less, leading to cost savings. Unlike German Equatorial mounts, there are no meridian flips to deal with, and no large protruding counterweights to create a dangerous hazard in a public observatory. Alt/Az is more intuitive to use and no polar alignment is needed. 

L-Series Mount Features:

  • Direct-drive motors on each axis for smooth, fast, and virtually silent movement of the telescope.
  • Load capacity of up to 200 pounds. 
  • Slew speeds up to 50 degrees per second
  • High-resolution encoders on each axis for precise positioning with feedback to counteract gusts of wind.
  • Sidereal tracking accuracy of <0.30 arcseconds RMS over 5 minutes.  
  • Zero backlash
  • Zero periodic error
  • PointXP mount modelling software
  • Enclosed electronics and through mount cabling for neat cable management with easy to access panels. 
  • PWI4 telescope control with PointXP mount modeling software. 
  • Can be configured either AZ or EQ. 
  • Optional dual mounting with additional dovetail bracket. 

Additional Included Items: 

  • Heating elements for dew prevention, heating pads on the primary and secondary mirror require the 600195 Delta-T controller sold separately. 
  • OTA cover to protect the primary and interior of the optical tube. 
  • Flashdrive containing all software and instructions for collimation and spacing the primary to the secondary. A second flashdrive contains PWI4 software and installation instructions. 
  • Hardware: 6 1/2-13x1 1/4" socket head cap screws to bolt the mount to th e pier or wedge.  6 1/2-13 washers.   1 extended length shoulder bolt for RA axis to EQ wedge alignment. 
  • 1 16' USB cable for computer connection. 
  • 1 120VAC power cable to power the mount. 
  • Standard Allen key set
  • Game pad for mount control while visually obvserving. 

CDK400 System Specifications: 


Optical Design Corrected Dall Kirkham
Aperture 17 inch 432mm
Focal Length 2939mm
Focal Ratio f/6.8
Central Obstruction 23.7% by surface area: 48.6% of the primary mirror diameter
Back Focus from Mounting Surface 10.32 inch (262.33mm)
Back Focus from Racked in Focuser 7.24 inch (184mm)
Weight 106 pounds
OTA Length  42 inches (1067mm)
Optical Performance 6.5 microns RMS at 21mm and 9.6 micron at 26mm off axis
Optical Tube Material and Construction Carbon fiber trusses with an aluminum shroud on the lower cage
Optical Field of View 70m image circle
Secondary Mirror Diameter 190mm (7.48 inch)
Secondary Mirror Material Fused silica quartz
Secondary Mirror Shape Spherical
Secondary Mirror Coating Enhanced Aluminum - 96%
Primary Mirror Diameter 17 inch (432mm)
Primary Mirror Outer Diameter 17.5 inch (445mm)
Primary Mirror Shape Prolate ellipsoid
Primary Mirror Material Fused silica quartz
Primary Mirror Coataing Enhanced Aluminum 96%
Lens Group Diameter 105mm (4.13 inch)
Number of Lenses 2
Coating Broadband AR Coatings (less than 0.5% reflected from 400 - 700nm)


L500 Mount Specifications: 

Type Alt-Azimuth/ Equatorial Direct Drive mount
Weight 257 pounds
Component Weights Azimuth base = 121 pounds, fork arm = 136 pounds
Max. Load Capacity 200 pounds
Latitude Range 0 to 90 degrees, Northern and Southern hemispheres
Cable Management Through mount cabling with easy to access panels
Swing Through Length (from Altitude Axis) 25.62"
Control Electronics PWI dual axis control
User Interface PWI4 with PointXP
Homing Sensors Included for finding home postition at start up. 
Slew Rate 20 degres standard, 50 degrees per second maximum, both axes
Power Requirement Accepts 120 to 240 VAC. Supplied with 120 VAC 15A IEC type B regulated power supply. 
Motor Control Industrial grade brushless motor control system and built in electronics 
Motor - Azimuth and Altitude Direct Drive 3 Phase Axial Flux Torque motors
Encoder - Azimuth and Altitude 152mm stainless steel encoder ring with reader built into the azimuth and altitude axes.  18,800,000 counts per revolution. (0.069 arcsecond resolution). 
Motor Torque Approx 20 ft. Lbs. continuous: 50 ft lbs peak
Drive Electronics  Industrial grade off the shelf brushless motor drives for each axis with custom designed interface 
Telescope Control Software

PWI4 with PointXP mount odeling software. HTTP and ASCOM control interfaces. Maxim DL is required for camera control with using PWI4 modeling. 

Pointing Accuracy

<10 arcsecond RMS with PointXP model

Pointing Precision

2 arcseconds at sidereal velocity

Tracking Accuracy

<0.3 arcseconds over a 5 minute period at sidereal velocity

System Natural Frequency

10 Hz or greater

Shipping Informatione

The crated weight of this system is 225 pounds, 30x37x58 inches.  The CDK400 is an oversize and heavy crated shipment that does require air, ship or truck freight delivery.  At this time our website is not able to calculate shipping rates for freight You will be contacted to discuss shipping options and crating fees for your order.  If you require a quote at any time prior to placing an order, please reach out to us at [email protected]


1 year warranty on optics and 2 years on mechanical 

More Information
Brand PlaneWave Instruments
Free Shipping Does Not Qualify for Free Shipping
Aperture 17" (432mm)
Case Included No
Focal Length 2939mm
Focal Ratio F/6.8
Focus Type None, ready to accept user choice of focuser.
Finderscope Included No
Diagonal Included No
Optical Tube Material Carbon Fiber
Highest Useful Magnification 864x
Resolution - Dawes 0.04 arcseconds
LIght Gathering Power (Compared to the Human Eye) 3809x
Secondary Mirror Obstruction By Diameter 23.7%
Secondary Mirror Obstruction By Area 48.6%
Optical Coatings Aluminum
Optical Tube Length 1067mm
Optical Tube Weight 106 pounds
Included Dovetail D series with expansion joint
Mount Load Capacity 200 pounds
Accessory Tray Included? No
Counterweights Included No
Adjustable Legs? No
Slew Speeds 20 degrees per second standards, up to 50 degrees per second max on both axes
Mount Motor Drive Direct Drive
Includes Autoguide Port Yes
USB Port Yes
Power Requirements Accepts 120 to 240 VAC, supplied with 120 VAC 15 IEC Type B regulated power adapter
Computerized Hand Controller Yes, for manual control during visual use
Included Software PWI4 with PointXP mount modeling
Periodic Error Correction No
Total System Weight 363 pounds
Warranty 1 year on optics and 2 years on mechanical
In The Box
  • CDK17 Optical Tube
  • L500 Direct Drive Mount
  • 6 1/2-13x 1 1/4” socket head cap screws to bolt the mount to the pier or wedge.
  • 6 1/2-13 washers
  • 1 extended length shoulder bolt for RA axis to EQ wedge alignment
  • 16 ft. USB cable
  • 120 VAC Power Cable
  • Standard Allen Key Set
  • Flashdrive containing software and instructions
  • 3/8 socket for RA balance leadscrew
  • Gamepad for visual observing control
  • CDK17 Optical Tube
  • L500 Direct Drive Mount
  • 6 1/2-13x 1 1/4” socket head cap screws to bolt the mount to the pier or wedge.
  • 6 1/2-13 washers
  • 1 extended length shoulder bolt for RA axis to EQ wedge alignment
  • 16 ft. USB cable
  • 120 VAC Power Cable
  • Standard Allen Key Set
  • Flashdrive containing software and instructions
  • 3/8 socket for RA balance leadscrew
  • Gamepad for visual observing control
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