PlaneWave CDK17 Optical Tube

PlaneWave CDK17 Optical Tube

PlaneWave CDK17

PlaneWave 17 inch CDK 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. 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 the large capacity 3.5 inch Hedrick focuser.

The CDK (Corrected Dall-Kirkham) Optical Design is an innovative solution for unsurpassed astroimaging quality at an affordable price. The CDK telescope design provides excellent 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.

This no-compromise design is unique in making the optical alignment forgiving and collimation very easy. This guarantees the user the best possible performance from the telescope. 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). The CDK design will give you pinpoint stars from the center to the corner of the field of view.

Fused Silica Glass Option: Fused silica is a synthetic amorphous silica glass of the highest purity and one of the most transparent glasses made. The optical and thermal properties of fused silica are superior to other types of glass due to its purity. Its transmission and homogeneity exceed those of crystalline quartz without the problems of temperature instability inherent in the crystalline form.

Fused Silica has a coefficient of thermal expansion six times lower than Borosilicate (Pyrex) glass, which means that as fused silica cools down, it preserves its shape to a high degree of accuracy. This translates into consistent optical performance and unchanging focus over temperature changes.

With its high melting temperature (~1,600 degrees Celsius), a very low coefficient of thermal expansion and resistance to thermal shock, Fused Silica is the material of choice for professional observatories as well as various scientific applications.

Cost: Adds $2,500 to the base price.


Starting at $22,000
PlaneWave CDK17 Brochure
PlaneWave Videos


Aperture: 17 inch (432 mm)

Focal Length: 2939 mm (115.71 inch)

Focal Ratio: f/6.8

Central Obstruction: 23.7% by surface area; 48.6% of the Primary Mirror Diameter

Back Focus from Mounting Surface: 10.24 inch (260 mm)

Back Focus from Racked in Focuser: 7.24 inch (184 mm)

Weight: 106 lbs (48 kg)

OTA Length: 42 inch (1067 mm)

Upper Cage: Carbon Fiber Truss

Lower Cage: Carbon Fiber Truss with Carbon Fiber Light Shroud

Optical Performance 6.5 micron rms at 21mm and 9.6 micron at 26mm off-axis

Overall Dimensions: Overall Dimensions (PDF)

Optimal Field of View: 70mm Image Circle


Crated Weight: 225 lbs (102.1 kg)

Crate Width: 30 inch (762 mm)

Crate Height: 37 inch (940 mm)

Crate Length: 58 inch (1,473 mm)

Primary Mirror

Diameter: 17.5 inch (445 mm)

Aperture: 17 inch (432 mm)

Focal Ratio: f/3.24

Mounting: Laser Collimated and Permanently Fixed

Material: Precision Annealed Pyrex

Shape: Prolate Ellipsoid

Coating: Enhanced Aluminum - 96%

Secondary Mirror

Diameter: 7.48 inch (190 mm)

Material: Precision Annealed Pyrex

Shape: Spherical

Coating: Enhanced Aluminum - 96%

Lens Group

Diameter: 105 mm (4.13 inch)

Number of lenses: 2

Coating: Broadband AR Coatings (less than .5% reflected from 400 to 700nm)

Standard Features

Carbon Fiber Truss 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

Cooling Fans: Three fans blow out of the optical tube pulling air though the telescope and by the primary mirror. This helps the telescope to reach thermal equilibrium quickly. The fans are controlled by a switch on the optical tube or can be conrolled by a computer if the optional Electronic Focus Accessory (EFA Kit) is purchased.

Included Accessories

Ronchi Spacer (600341 & 600343): This spacer is used for setting the primary to secondary spacing. It has an 1-1/4 inner diameter and may be used with 1-1/4 oculars for collimation.

Ronchi Ocular: This ocular is a Ronchi screen used for setting the primary to secondary spacing.

Primary Mirror Cover: The Primary Mirror Cover protects the primary mirror.

Planewave Thumb Drive: Containing all documentation and software for collimation and spacing

12VDC Power Supply (18778): Provides power for the fans (Not included for European Orders)

Wrench Set (5812A35): English Hex Wrenches (European Orders Only)