PlaneWave 20 inch CDK Optical Tube Assembly

PlaneWave 20 inch CDK Optical Tube Assembly
  • $32,500.00

 


The PlaneWave Instruments CDK20 is a 20 inch (0.51 m) f/6.8 Corrected Dall-Kirkham Astrograph telescope. The CDK20 has a dual carbon-fiber truss design, with 3 cooling fans ejecting air from the back of the telescope. The CDK20 covers a 52 mm field of view without any field curvature, off-axis coma, or astigmatism. The instrument weight is 140 lbs (64 kg) and comes standard with a back plate retaining ring ready to accept the focuser of your choice.

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.

Recommended Configuration

CDK20 with Ascension 200HR Mount

$32,500
CDK20 Optical Tube (200101)
$23,500
Ascension 200HR German Equatorial Mount (A200110)
$1,200
3 Counterweights, 40 lbs each, 1.875" shaft (600111)
$225
8" Counterweight Extension Shaft (A200-142)
n/c
Dovetail Clamp (200919)
$57,425
Total Price
 
PlaneWave System
Aperture 20 inch (508 mm)
Focal Length 3454 mm (135.98 inch)
Focal Ratio f/6.8
Central Obstruction 39% of the Primary Mirror Diameter
Back Focus from Mounting Surface 8.8 inch (224 mm)
Back Focus from Racked in Focuser 5.8 inch (147 mm)
Weight 140 lbs (63.5 kg)
Upper Cage Carbon Fiber Truss
Lower Cage Carbon Fiber Truss with Carbon Fiber Light Shroud
Optical Performance 16.5mm off-axis: 5 micron RMS spot size; 21mm off-axis: 6.5 micron RMS spot size; 26mm off-axis: 11.4 micron RMS spot size
Overall Dimensions 47 inch (1,194 mm) long X 27 inch (686mm) wide X 27.5 inch (699mm) high
PlaneWave Primary Mirror
Diameter 20.5 inch (521 mm)
Aperture 20 inch (508 mm)
Focal Ratio f/3
Mounting Laser Collimated and Permanently Fixed
Material Precision Annealed Pyrex
Shape Prolate Ellipsoid
Coating Enhanced Aluminum - 96%
PlaneWave Secondary Mirror
Diameter 7.5 inch (191 mm)
Material Precision Annealed Borosilicate
Shape Spherical
Coating Enhanced Aluminum - 96%
PlaneWave Lens Group
Diameter 90 mm (3.54 inch)
Number of Lenses 2
Coating Broadband AR Coatings (less than .5% reflected from 400 to 700nm)
PlaneWave Standard Features
Design Carbon fiber truss design that minimizes thermal expansion which causes focus shift with changes in temperature
Dovetail The massive PlaneWave dovetail supports the optical tube to provide rigidity. A matching dovetail clamp is available to install on various mounts.
Light Shroud Carbon fiber lower light shroud that protects the primary mirror from damage and stray light
Dovetail Expansion 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.
PlaneWave Shipping
Crated Shipping Weight 291 lbs (132.0 kg)
Crate Dimensions 32 inch (813 mm) wide X 36 inch (914 mm) high X 59 inch (1,499 mm) long
PlaneWave Included Accessories
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 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)

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