PlaneWave CDK 14" Telescope Optical Tube Assembly

Sold out
£15,140.00
SKU 1323214
  • A 14"/0.36m visual and astrographic telescope
  • Uses PlaneWave's Corrected Dall-Kirkham (CDK) optical design
  • 70mm diameter imaging circle
  • No field curvature, off-axis coma, or astigmatism.
  • Carbon fibre truss-tube for low thermal expansion, rigidity and weight saving.
  • Two optical glass options available
Introduction

PlaneWave's CDK14 is a 14-inch (0.36 m) aperture f/7.2 telescope that is very well suited for astro-imaging as well as for visual use.

PlaneWave CDK14

The CDK14 telescope utilises the Corrected Dall-Kirkham (CDK) optical design, developed by Dave Rowe, that provides excellent imaging possibilities 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-Chrétien design making the CDK an innovative solution for unsurpassed astro-imaging quality at an affordable price. 

The end result, at the image plane of the CDK14, will give you pinpoint stars from the center to the corner of its 70mm field of view without any field curvature, off-axis coma, or astigmatism. The no-compromise optical design is unique in making the optical alignment forgiving and collimation very easy which guarantees the user the best possible performance from the telescope. 

The CDK14 features a dual carbon-fibre truss design, with 3 cooling fans blowing air throughout the back of the telescope, The instrument weighs 22kg (48 lbs) and comes as standard with a back plate retaining ring ready to accept the focuser of your choice. The relatively low weight of the CDK14 means it can be used, with additional accessories, on medium sized mounts such as the 10Micron GM2000 (or above) or the Paramount MX+ (and above).

Telescope Features

The CDK14 telescope is an open truss tube design for a rigid, but lightweight structure, and for quick thermal cooling. The truss tube utilises a carbon fibre frame which minimises thermal expansion that can cause focus shift with changes in temperature. The carbon fibre truss tube design also promotes quick thermal cooling.

CDK Carbon Fibre Truss Tube Poles

The CDK's carbon fibre truss poles 

To create the telescope's baffles, Planewave uses digital 3D printing technology. Their 3D printers add successive layers of material to construct a baffle system with precision. These internal stray light baffles minimise vignetting and maximise image contrast.

CDK 3D Printed Baffle

3D Printed Primary Baffle

To mount the CDK14 onto a mount, PlaneWave supplies the CDK with a dovetail bar. The CDK features a dovetail expansion joint that allows for the difference in thermal expansion between carbon fibre and aluminium. This expansion joint allows the aluminium dovetail expand and contract without stressing the carbon fibre lower truss.

CDK Dovetail Expansion Joint

Dovetail expansion joint

To help the primary mirror to cool, there are three cooling fans that blow air inside the back of the telescope. Furthermore, internal diverting fins circulate air flow behind the mirror for even cooling to help the telescope reach thermal equilibrium quickly. The fans are controlled by a computer if the optional Electronic Focus Accessory (EFA Kit) is purchased.

CDK Rear Cooling Fans

 Cooling Fans at the rear of the CDK14

For dew prevention, the CDK14 is internally wired with polyimide film heater pads and temperature sensor, ready to be controlled with the optional Delta-T controller.

CDK Internal Mirror Heating Pads making the CDK Delta-T Ready

CDK14 Internal dew heater pads
Optical Features

The Ritchey Chrétien (RC) optical design has long been "the standard" in high end imaging telescopes due to its use in many professional observatories. The RC is successful in eliminating many of the problems that plague many other optical designs, namely off-axis coma, however the RC design does nothing to eliminate the damaging effects of off-axis astigmatism and field curvature. The RC design is also very difficult, and therefore expensive, to manufacture and optically align. 

CDK Optical Design

Optical Design of the PlaneWave Corrected Dall-Kirkham (CDK)

 The CDK design tackles the "off-axis coma problem" by integrating a pair of correcting lenses into a two mirror design. The beauty is that this design also corrects for astigmatism and field curvature. Because the lenses are relatively close to the focal plane (unlike the Schmidt corrector plate found in various Schmidt Cassegrain designs), and because these lenses work together as a doublet, there is no chromatic aberration. The CDK offers a wide aberration-free, flat field of view that allows the user to take full advantage of the very large imaging chip cameras in the market place today.

CDK Spot Diagram for CDK14

In the image above, on the left column, the diagram shows a diffraction simulation for 14" CDK optics on the optical axis, and with a distance of 13 and 35mm from the optical axis. The right column shows the calculated spot diagram with small squares being 9 microns wide. The diameter of a star at the edge of the flat field corresponds to the pixel size of current large-format CCD chips and the imaging quality of the optics is limited only by the seeing conditions and the quality of the tracking. The large field of view of 70mm diameter offers enough tolerance for CCD cameras with ever increasing-sized sensors.

Having an aberration free telescope design means nothing if the optics cannot be aligned properly. Many Ritchey owners never get to take full advantage of their instrument’s performance because the Ritchey is very difficult to collimate. Aligning the hyperbolic secondary mirror’s optical axis to the optical axis of the primary mirror is critical in the Ritchey design, and the tolerances are unforgiving. The secondary mirror of the CDK design is spherical. It has no optical axis and so the centering tolerance of the CDK secondary mirror is comparatively huge. With the help of some very simple tools, the CDK user will be able to set the secondary spacing, collimate the optics and begin enjoying the full performance potential the instrument has to offer within a few minutes.

There are 2 options available for the type of optical glass used in the CDK14 telescope: Borosilicate and fused Silica:

Below are a few images taken with a CDK14 to show how well they perform. 

M13 Globular Cluster

M51Specifications

OPTICAL SYSTEM

Optical Design Corrected Dall-Kirkham (CDK)
Aperture 14 inch (356mm)
Focal Length 2563mm (101 inch)
Focal ratio F/7.2
Central Obstruction 23.5% by surface area; 48.5% by diameter
Back Focus from Mounting Surface 11.09 inch (282 mm)
Weight 48 lbs (22 kg)
OTA Length 35 inch (889 mm)
Optical Performance 3.1 micron RMS at 13mm off-axis; 6.0 micron RMS at 35mm off-axis - Spot Diagram
Upper Cage Carbon Fiber Truss
Lower Cage Carbon Fiber Truss and Light Shroud
Optimal Field of View 70mm Image Circle

 

SECONDARY MIRROR

Diameter 165 mm (6.5 inch)
Material Precision Annealed Borosilicate
Shape Spherical
Coating Enhanced Aluminum - 96%

 

PRIMARY MIRROR

Optical Diameter 14 inches (355.6)
Outer Diameter 14.5 inches (468.3mm)
Shape Prolate Ellipsoid
Material Precision Annealed Borosilicate or Fused Silica
Coating Enhanced Aluminum - 96%

 

LENS GROUP

Diameter 95mm (3.7 inch)
Number of lenses Two
Coating broadband AR Coatings (less than .5% reflected from 400 to 700nm)

 


STANDARD FEATURES

CDK Optics The Corrected Dall-Kirkham design yields a perfectly flat field free from off-axis astigmatism, coma and defocus.
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 cooling fans blow air inside the back of the telescope. This helps the telescope to reach thermal equilibrium quickly. The fans are controlled by a computer if the optional Electronic Focus Accessory (EFA Kit) is purchased.
Delta-T Ready For added dew prevention, the CDK14 is internally wired with polyimide film heater pads and temperature sensor, ready to be controlled with the optional Delta-T controller.

SHIPPING

Crated Shipping Weight  225 lbs
Crate Width  31 inches
Crate Height  26 inches
Crate Length  53 inches

INCLUDED ACCESSORIES

Ronchi Spacer (600341 & 600344) This spacer sits in place of a focuser and 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 Provides power for the fans (Not included for European Orders)
Wrench Set (5812A35) English Hex Wrenches (European Orders Only)

Downloads

Camera Adapters Diagrams

Software

Drawings & Diagrams

Instructions

Helpful Tools

You recently viewed

Clear recently viewed