PlaneWave CDK24/PW24-RC Optical Tube

PlaneWave CDK24/PW24-RC Optical Tube

PlaneWave CDK24/PW24-RC

The PlaneWave Instruments CDK24/PW24-RC is a 24 inch (0.61 m) f/6.5 Astrograph telescope with either Corrected Dall-Kirkham (CDK) or Ritchey-Chrétien (RC) optics. The telescope has a dual truss design, with 3 cooling fans for the back of the primary mirror and 8 fans for the front surface of the primary mirror. The CDK24/PW24-RC covers a 70 mm field of view without any field curvature, off-axis coma, or astigmatism. The instrument weight is 240 lbs (109 kg) and comes standard with the large capacity 3.5" Hedrick focuser.

The CDK 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 $10,000 to the base price.


Ritchey-Chrétien Optics Option: In certain applications such as photometry and spectroscopy, refractive lenses could influence scientific results. The PW24-RC in its native format (no field flattening lenses) uses only a primary and secondary mirror with reflective coatings. This can be useful when making observations primarily on-axis and wide field imaging is not a concern.

Cost: Adds $15,000 to the base price.


Starting at $50,000
Corrected Dall-Kirkham / Ritchey-Chrétien Optics Comparison
PlaneWave CDK24 Brochure
PlaneWave Videos


Optical Design: Corrected Dall-Kirkham (CDK) or Ritchey-Chrétien (RC)

Aperture: 24 inch (610 mm)

Focal Length: 3962 mm (155.98 inch)

Focal Ratio: f/6.5

Central Obstruction: 47% of the Primary Mirror Diameter

Back Focus from Mounting Surface: 14.1 inch (358 mm)

Back Focus from Racked in Focuser: 5.81 inch (148 mm)

Weight: 240 lbs (108.9 kg)

OTA Length: 56 inch (1,422 mm)

OTA Width: 31 inch (787 mm)

OTA Height: 35 inch (889 mm)

Upper Cage: Carbon Fiber Truss

Lower Cage: Carbon Fiber Truss with Aluminum Light Shroud

Optimal Field of View: 70 mm (58 arcminute)


Crated Shipping Weight: 500 lbs (226.8 kg)

Crate Width: 40 inch (1,016 mm)

Crate Height: 48 inch (1,219 mm)

Crate Length: 78 inch (1,981 mm)

Primary Mirror

Diameter: 24.5 inch (622 mm)

Aperture: 24 inch (610 mm)

Focal Ratio: f/3.2

Mounting: Laser Collimated and Permanently Fixed

Material: Precision Annealed Borosilicate or Fused Silica

Shape: Prolate Ellipsoid (CDK); Hyperbolic (RC)

Coating: Enhanced Aluminum - 96%

Secondary Mirror

Diameter: 9.45 inch (240 mm)

Material: Precision Annealed Borosilicate or Fused Silica

Shape: Spherical (CDK); Hyperbolic (RC)

Coating: Enhanced Aluminum - 96%

Lens Group (CDK)

Diameter: 135 mm (5.31 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: The CDK24 has two different cooling schemes. First there are three fans behind the primary mirror that blow air out of the optical tube pulling air though the telescope and by the primary mirror. This helps the telescope to equilibrate quickly. The second scheme is that there are 4 fans placed around the face of the primary mirror to equilibrate the face of the mirror and to keep a laminar air flow above the telescope's light path. The two schemes can be controlled separately with the included switches on the optical tube or can be controlled by a computer if the optional Electronic Focus Accessory (EFA Kit) is purchased.

Included Accessories

CDK24 Focus Spacer (240343): This 5.3" long spacer may be installed between the backplate and the focuser to take up some of the CDK24's extra backfocus and reduce the torque placed on the focuser mechanism. This spacer is sized such that the backfocus distance behind the focuser will match that of the CDK20.

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.

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)