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CDK20 f/7.7 Optical Tube Assembly

SKU: 200127Q Categories: , ,

$34,000.00

The CDK20 f/7.77 from PlaneWave Instruments stands as a pinnacle of engineering excellence, tailored for serious astrophotographers and astronomers who demand precision and performance. With its advanced technology and high-quality design, the CDK20 f/7.77 delivers outstanding images for a wide range of advanced observational and scientific applications.

*Price excludes shipping and crating. See our crating and pricing policy for full details.

Key Features Overview

The CDK20 f/7.77 is characterized by its exceptional specifications and features:

  • 20-inch (508 mm) aperture
  • 3951 mm focal length
  • f/7.77 focal ratio
  • 269.49 mm back focus from mounting surface
  • Perfectly flat field across the entire 52mm image circle
  • No off-axis coma or astigmatism
  • Rock-solid fused silica mirrors with low thermal expansion
  • Lightweight and rigid carbon fiber optical tube assembly
About the CDK20 f/7.7 Optical Tube Assembly

CDK20 f/7.77’s Key Features

Large Aperture and Moderate Focal Ratio

The CDK20 f/7.77 features a 508 mm aperture and a high f/7.77 focal ratio. This configuration provides excellent light-gathering efficiency and image scale, making it ideal for detailed lunar, planetary, and deep-sky imaging.

Advanced Optical Design

The CDK20 f/7.77 has a state-of-the-art Corrected Dall-Kirkham optical system that offers exceptional image clarity. This design eliminates off-axis coma and astigmatism and delivers a perfectly flat field, ensuring that images are crisp and detailed across the entire field of view with minimal post-processing required.

Robust Mechanical Structure

Constructed with a carbon fiber optical tube, the CDK20 f/7.77 is lightweight and sturdy. Its thermal expansion coefficient ensures minimal focus shift with temperature changes, making it suitable for extended observing sessions under diverse environmental conditions.

High-Performance Mirrors and Coatings

Featuring fused silica mirrors, the CDK20 f/7.77 maintains precise optical alignment and surface accuracy, even with temperature fluctuations. Its high-quality coatings maximize light transmission and minimize stray light, optimizing performance for critical observational tasks.

Thermal Management

The CDK20 f/7.77 includes cooling fans and a Delta-T ready system to achieve thermal equilibrium rapidly. These features reduce air turbulence within the tube, minimizing image distortion and maintaining consistent imaging quality.

Integrated Dew Control

The telescope incorporates advanced dew prevention technology with heater pads controlled by PlaneWave’s software. This ensures optical surfaces remain clear of condensation in humid conditions, maintaining clear and consistent imaging performance.

Application-Specific Benefits

Astrophotography

With its precise focal ratio and large image circle, the CDK20 f/7.77 allows astrophotographers to capture detailed and expansive views of the cosmos, providing incredible detail and clarity.

Astronomy Research

The stable and precise imaging capabilities of the CDK20 f/7.77 make it an invaluable tool for academic institutions and observatories engaged in sophisticated astronomical research, including detailed photometric studies and complex deep-sky surveys.

Visual Observations

The CDK20 f/7.77 excels in visual observation, offering bright and crisp views ideal for star parties and serious visual astronomy. The telescope's significant aperture and excellent optical quality provide stunning views of planetary, lunar, and deep-sky objects, making every viewing session a memorable experience.

Space Situational Awareness (SSA) and Space Domain Awareness (SDA)

The CDK20 also lends itself to Space Situational Awareness and Space Domain Awareness applications. Its capability to provide detailed observations can be essential for tracking and monitoring satellites and other space debris, contributing valuable data for space traffic management and safety initiatives.

Specifications

CDK20 f/7.7 Optical Tube Assembly

OPTICAL SYSTEMS
LENS GROUP
SECONDARY MIRROR
PRIMARY MIRROR
included items
Aperture 508 mm (20")
Focal Length 3951 mm (156")
Focal Ratio f/7.7
Central Obstruction 39% of the Primary Mirror Diameter
Back Focus from Mounting Surface 269.24 mm (10.6")
Weight 140 lbs (63.5 kg)
OTA Length 1194 mm (47")
Optical Design Performance 1.5-micron RMS on-axis, 3.8-micron RMS at 12 mm off-axis, 6.0-micron at 21 mm off-axis
Upper Cage Carbon fiber truss
Lower Cage Carbon fiber truss and light shroud
Diameter 90 mm (3.54")
Coating Broadband AR Coatings (less than .5% reflected from 400 to 700 nm)
Optical Diameter 508 mm (20")
Diameter 191 mm (7.5")
Material Fused silica (quartz)
Shape Spherical
Coating Enhanced Aluminum - 96%
Optical Diameter 508 mm (20")
Outer Diameter 521 mm (20.5")
Shape Prolate Ellipsoid
Material Fused Silica (quartz)
Coating Enhanced Aluminum - 96%
Included Items Heating Elements for Dew Prevention - The heating pads on the primary and secondary mirror require the 600195 Delta-T controller sold separately
OTA Cover - To protect the primary mirror and inside of the optical tube
Flashdrive - Contains software and instructions for collimation and spacing the primary to secondary mirror
Wrench Set (5812A35) - Standard hex wrenches (European orders only)

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*Price excludes shipping and crating. See our crating and pricing policy for full details.

Key Features Overview

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Electronic Focus Accessory (EFA) Kit
  • The EFA kit automates focusing on the optional Hedrick Focuser, or IRF90 rotating focuser.
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  • Ensure you have the proper EFA kit selected for your telescope below.
    • 125901-Kit is for CDK12.5 OTAs.
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Fabric Light Shroud

This is a spandex fabric light shroud that blocks out stray light and minimizes dust on the primary mirror.

Available for the CDK14, CDK17, CDK20, CDK24, and CDK700.

$140.00$790.00
Delta T Heater
  • The Delta T controller is an optional accessory for dew prevention on CDK14 through CDK24 OTAs and the CDK700 system.
  • CDK12.5 to CDK24 and CDK700 telescopes come with primary and secondary mirror dew heating pads (CDK700 adds tertiary mirror heating), which are ready to accept the Delta T controller.
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Telescope Dovetail Saddles

The Keller EZ Saddle (600182) accepts Losmandy D-style dovetail rails such as the CDK12.5, CDK14, and DeltaRho 350. This saddle comes standard with the L-350 mount and can also be attached to the outside arm of any L-series mount for dual-mounted OTA configurations.

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IRF90 – Integrated Rotating Focuser
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Piggyback Dovetail Bars
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Hedrick Focuser
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L-500/L-600 Equatorial Wedge
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Visual Adapter – CDK20/24

This 3.5″-2″ Visual Adapter, for the CDK20 and CDK24, slides into the optional 3.5″ Hedrick Focuser.

  • The adapter steps the 3.5″ opening down to 2″ for standard 2″ accessories.
  • The adapter also adds some additional spacing to optimize the use of a 2″ diagonal so focus is reached with most eyepieces.
$160.00
Finderscope and Mounting Bracket

The back plate on all of the CDK models has four mounting positions for a finder mounting plate.

  • The finder mounting plate attaches to the back plate of the telescope and the quick-release finder bracket attaches to the mounting plate.
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2 inch Mirror Diagonal
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  • Resulting images through this diagonal are brighter and “whiter”
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  • 2″ filter anti-reflection threads in the diagonal let you attach filters to the diagonal instead of moving from eyepiece to eyepiece
  • Brass clamp ring holds 2″ eyepieces and accessories firmly in place without marring the barrels
  • Included 2″ to 1.25″ HiHat Adapter is of same high quality in make and materials
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Mounting Bracket for Finderscopes
  • This is an L-shaped bracket that attaches in four different places on the back of any of the CDK models.
  • This is used to mount a finderscope or some other accessory.
  • Two 1/4-20 screws provided attach the bracket to the backplate of the telescope and two 10-32 threaded holes spaced at 1.450″ can be used to mount accessories too.
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Reducer 0.66x CDK20 / CDK24

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See the CDK20 f/7.7 Optical Tube Assembly in action
CDK20 f/7.7 Optical Tube Assembly Astroimages