24 inch CDK Optical Tube Assembly

24 inch CDK Optical Tube Assembly

Part   240101

Introducing the PlaneWave Instruments CDK24, a 24 inch (0.61 m) f/6.8 Corrected Dall-Kirkham Astrograph telescope. The CDK24 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 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 (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-Chrétien 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.
The CDK Optical Design

FEATURES AND SPECIFICATIONS

SYSTEM

Aperture	24 inch   (610 mm)
Focal Length	4145 mm   (163.19 inch)
Focal Ratio	f/6.8
Central Obstruction	41% of the Primary Mirror Diameter
Back Focus from Mounting Surface	13.45 inch   (342 mm)
Back Focus from Racked in Focuser	9.45 inch   (240 mm)
Weight	240 lbs   (108.9 kg)
OTA Length	55 inch   (1,397 mm)
OTA Width	32 inch   (813 mm)
OTA Height	37 inch   (940 mm)
Upper Cage	Carbon Fiber Truss
Lower Cage	Carbon Fiber Truss with Aluminum Light Shroud
Optimal Field of View	70 mm (58 arcminute)

PRIMARY MIRROR

Diameter	24.5 inch   (622 mm)
Aperture	24 inch   (610 mm)
Focal Ratio	f/3
Mounting	Laser Collimated and Permanently Fixed
Material	Precision Annealed Borosilicate
Shape	Prolate Ellipsoid
Coating	Enhanced Aluminum - 96%

SECONDARY MIRROR

Diameter	9.45 inch   (240 mm)
Material	Precision Annealed Borosilicate
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
Lower Light Shroud	Protects the primary mirror from damage and stray light
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
3.5 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. It accepts an optional dial indicator and PlaneWave’s EFA Kit to control many electronic accessories. The draw tube travel is 1.3 inch. Image 1 Image 2 Drawing of Flange Drawing of Draw Tube
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 8 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.

SHIPPING

Crated Shipping Weight	500 lbs   (226.8 kg)
Crate Width	40 inch   (1,016 mm)
Crate Height	45 inch   (1,143 mm)
Crate Length	65 inch   (1,651 mm)

INCLUDED ACCESSORIES

3.5\" to 2\" Adapter (200349)	Adapts the 3.5\" inner diameter of the focuser to a standard 2\" inner diameter. This adapter is necessary when setting the primary to secondary spacing. The 200399 Visual 3.5\" 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.
Primary Mirror Cover	The Primary Mirror Cover protects the primary mirror.
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)