PlaneWave CDK125 Optical Tube

PlaneWave CDK125 Optical Tube

PlaneWave CDK125

The PlaneWave Instruments CDK125 is a 12.5 inch (0.32 m) f/8 Corrected Dall-Kirkham Astrograph telescope. The telescope has a closed carbon fiber tube, with 3 cooling fans ejecting air from the back of the telescope. The CDK12.5 covers a 52 mm field of view without any field curvature, off-axis coma, or astigmatism. The instrument weight is 46 lbs and comes standard with the large capacity 2.75 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 $500 to the base price.


Starting at $9,990
PlaneWave CDK12.5 Brochure
PlaneWave Videos


Aperture: 12.5 inch (318 mm)

Focal Length: 2541 mm (100.04 inch)

Focal Ratio: f/8

Central Obstruction: 42% of the Primary Mirror Diameter

Back Focus from Mounting Surface: 10.445 inch (265 mm)

Back Focus from Racked in Focuser: 7.2 inch (183 mm)

Weight (includes manual-focuser and dovetail): 46 lbs (20.9 kg)

Weight (includes electronic-focuser and dovetail): 48.5 lbs (22.0 kg)

OTA Length: 31 inch (787 mm)

Optical Tube: Carbon Fiber

Overall Dimensions: Overall Dimensions (PDF)


Crated Weight: 163 lbs (73.9 kg)

Crate Width: 22 inch (559 mm)

Crate Height: 29 inch (737 mm)

Crate Length: 48 inch (1,219 mm)

Primary Mirror

Diameter: 13 inch (330 mm)

Aperture: 12.5 inch (318 mm)

Focal Ratio: f/3

Mounting: Laser Collimated and Permanently Fixed

Material: Precision Annealed Pyrex

Shape: Prolate Ellipsoid

Coating: Enhanced Aluminum - 96%

Secondary Mirror

Diameter: 4.65 inch (118 mm)

Material: Precision Annealed Pyrex

Shape: Spherical

Coating: Enhanced Aluminum - 96%

Lens Group

Diameter: 70 mm (2.76 inch)

Number of lenses: 2

Coating: Broadband AR Coatings (less than .5% reflected 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.

2.75 inch Hedrick focuser: Heavy duty no-slip focuser. The focus tube runs on 5 bearings and is driven by a leadscrew so there is no chance of slipping. Focus may be automated through a computer using PlaneWave's EFA Kit add-on. The draw tube travel is 1.3 inch. Hedrick focuser diagrams

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

2.75" to 2" Adapter (125355): Adapts the 2.75" inner diameter of the focuser to a standard 2" inner diameter. This adapter is necessary when setting the primary to secondary spacing. The 125399 Visual 2.75" to 2" adapter is an optional accessory that is designed to space a 2" diagonal for visual use.

Ronchi Spacer (200354): 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.

OTA Cover: The OTA cover is for closing the front of the tube to protect the primary mirror and the inside of the optical tube.

Printed Instructions: 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)