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Planewave - Company Information

PlaneWave Instruments was founded in 2006 by Richard Hedrick and Joseph Haberman, two former telescope engineers at Celestron, one of the largest telescope manufacturer worldwide. Richard Hedrick brings over 21 years of telescope design experience. As former Chief Technology Officer and previous owner of Celestron he was responsible for developing Celestron’s award winning Schmidt-Cassegrain computerized telescopes.

Joseph Haberman has over 20 years of experience in telescope design and worked at Celestron as an optical engineer and master optician. Getting a product like the CDK into the hand of serious imagers and amateur astronomers has been a shared vision of Hedrick and Haberman for many years.

PlaneWave Instruments is committed to providing observatory-class products for serious astronomers at an unprecedented value.

Planewave Instruments can be found in professional and advanced amateur observatories the world over and have become the scope of choice for many of the worlds best and most advanced astro imagers.

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Planewave - An Introduction to Large Aperture True Astrographs

Planewave are American manufacturers of Modified Dall Kirkham Cassegrain Instruments.

These instruments are designed and made to the highest standards with the advanced astro imager very much in mind.

The CDK [Corrected Dall-Kirkham] telescope is based on a new optical design developed by Dave Rowe. The goal of the design is to make an affordable astrographic telescope with a large enough imaging plane to take advantage of the large format CCD cameras of today. Most telescope images degrade as you move off-axis from either coma, off-axis astigmatism, or field curvature. The CDK design suffers from none of these problems. The CDK is coma free, has no off-axis astigmatism, and has a flat field. The design is a simple and elegant solution to the problems posed above. The CDK consists of three components: an ellipsoidal primary mirror, a spherical secondary mirror and a lens group. All these components are optimized to work in concert in order to create superb pinpoint stars across the entire 52mm or larger image plane.

See Optical Performance Image

Shown are two simulations showing the CDK’s stunning performance. The first is a diffraction simulation and the second is a spot diagram. In both simulations the small squares are 9×9 microns, about the size of a CCD pixel. In the diffraction simulation the star images on axis and off-axis are nearly identical. In the spot diagram 21mm off-axis the spot size is an incredible 6 microns RMS diameter. This means stars across a 52 mm image circle are going to be pinpoints as small as the atmospheric seeing will allow.
Both of the simulations take into consideration a flat field, which is a more accurate representation of how the optics would perform on a flat CCD camera chip. For visual use some amount

See Comparison Image between CDK and RCT

Comparison: CDK vs. Ritchey Chrétien
The simulations shown compares the optical performance of the CDK design to the Ritchey Chrétien (RC) design. The Ritchey design was popularized as an astroimaging telescope due to its use in many professional observatories. Although very difficult and expensive to manufacture and align, the Ritchey is successful in eliminating many of the problems that plague many other designs, namely off-axis coma. However the Ritchey does nothing to eliminate the damaging effects of off-axis astigmatism and field curvature.
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.
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.
The drastic difference in performance between the CDK and the RC is apparent. The biggest component that degrades the off-axis performance of the RC is the defocus due to field curvature. In many diagrams shown by RC manufacturers, the diagrams look better than this because they are showing a curved field. This is fine for visual use because the eye can compensate for some amount of curvature of field. But CCD arrays are flat and so in order to evaluate the performance a spot diagrams and/or diffraction simulations requires a flat field as shown.

Planewave CDK14 Corrected Dall Kirkham Astrograph

The PlaneWave Instruments CDK14 is a 14 inch (0.36 m) f/7.2 Corrected Dall-Kirkham Astrograph telescope. The CDK14 covers a 70 mm field of view without any field curvature, off-axis coma, or astigmatism.

The CDK14 is a lightweight carbon-fiber truss design weighing less than 50lbs, with 3 cooling fans blowing air throughout the back of the telescope. The CDK optical design is the innovative solution for unsurpassed astro-imaging quality at an affordable price.

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 CD

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.

Technical Specs:

Features:
Carbon Fiber Truss Design. Open truss tube design with carbon fiber frame minimizes thermal expansion
which causes focus shift with changes in temperature. Carbon fiber truss design also promotes quick thermal cooling and provides a Rigid, lightweight structure.

3D Printed Baffles.Planewave uses digital 3D printing technology to produce lightweight baffle tubes. 3D printers add successive layers of material to construct a baffle system with precision positioned internal stray light baffles to minimize vignetting and maximize image contrast.

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. Internal diverting fins circulate air flow behind the mirror for even cooling to help the telescope reach thermal equilibrium quickly. The fans are controlled with PWI PC software with the optional Electronic Focus Accessory (EFA Kit).

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.

£9,598.00

Planewave CDK 12.5"

The PlaneWave Instruments CDK12.5 is a 12.5 inch (0.32 m) f/8 Corrected Dall-Kirkham Astrograph telescope. The telescope has a closed carbon fiber tube, with 3 cooling fans ejecting air from the back of the telescope. The CDK12.5 covers a 52 mm field of view without any field curvature, off-axis coma, or astigmatism. The instrument weight is 46 lbs and comes standard with the large capacity 2.75 inch 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.

Vignetting and spot size plots

Spot and diffraction diagrams - click here

Overall Dimensions PDF

Technical Specs:

Aperture 12.5 inch (318 mm)
Focal Length 2541 mm (100.04 inch)
Focal Ratio f/8
Central Obstruction 42% of the Primary Mirror Diameter
Back Focus from Mounting Surface 10.445 inch (265 mm)
Back Focus from Racked in Focuser 7.2 inch (183 mm)
Weight (includes manual-focuser and dovetail) 46 lbs (20.9 kg)
Weight (includes electronic-focuser and dovetail) 48.5 lbs (22.0 kg)
OTA Length 31 inch (787 mm)
Optical Tube Carbon Fiber
Optical Performance Vignetting and Spot Size Plots
Spot and Diffraction Diagrams
Overall Dimensions Overall Dimensions (PDF)

PRIMARY MIRROR
Diameter 13 inch (330 mm)
Aperture 12.5 inch (318 mm)
Focal Ratio f/3
Mounting Laser Collimated and Permanently Fixed
Material Precision Annealed Pyrex
Shape Prolate Ellipsoid
Coating Enhanced Aluminum - 96%

SECONDARY MIRROR
Diameter 4.65 inch (118 mm)
Material Precision Annealed Pyrex
Shape Spherical
Coating Enhanced Aluminum - 96%

LENS GROUP
Diameter 70 mm (2.76 inch)
Number of lenses 2
Coating Broadband AR Coatings (less than .5% reflected from 400 to 700nm)

STANDARD FEATURES
Carbon Fiber Tube 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
2.75 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
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.

SHIPPING
Crated Shipping Weight 163 lbs (73.9 kg)
Crate Width 23 inch (584 mm)
Crate Height 31 inch (787 mm)
Crate Length 41 inch (1,041 mm)

INCLUDED ACCESSORIES
2.75" to 2" Adapter (125355) Adap ts the 2.75" inner diameter of the focuser to a standard 2" inner diameter. This adapter is necessary when setting the primary to secondary spacing. The 125399 Visual 2.75" 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.
OTA Cover The OTA cover is for closing the front of the tube to protect the primary mirror and the inside of the optical tube.
Printed Instructions For Collimation and Spacing
Wrench Set (5812A35) English Hex Wrenches

£17,598.00

Planewave 17 Inch CDK Optical Tube Assembly

The PlaneWave Instruments CDK17 is a 17 inch (0.43 m) f/6.8 Corrected Dall-Kirkham Astrograph telescope. The CDK17 has a dual carbon-fiber truss design, with 3 cooling fans ejecting air from the back of the telescope. The CDK24 covers a 52 mm field of view without any field curvature, off-axis coma, or astigmatism. The instrument weight is 94 lbs (43 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.

Technical Specs:

Aperture 17 inch (432 mm)
Focal Length 2939 mm (115.71 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 94 lbs (42.6 kg)
OTA Length 37 inch (940 mm)
Upper Cage Carbon Fiber Truss
Lower Cage Carbon Fiber Truss with Carbon Fiber Light Shroud
Optical Performance 6.5 micron rms at 21mm and 9.6 micron at 26mm off-axis
Vignetting and Spot Size Plots
Spot and Diffraction Diagrams
Overall Dimensions Overall Dimensions (PDF)

PRIMARY MIRROR
Diameter 17.5 inch (445 mm)
Aperture 17 inch (432 mm)
Focal Ratio f/2.6
Mounting Laser Collimated and Permanently Fixed
Material Precision Annealed Pyrex
Shape Prolate Ellipsoid
Coating Enhanced Aluminum - 96%

SECONDARY MIRROR
Diameter 6.25 inch (159 mm)
Material Precision Annealed Pyrex
Shape Spherical
Coating Enhanced Aluminum - 96%

LENS GROUP
Diameter 90 mm (3.54 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
Carbon Fiber Lower Light Shroud Protects the primary mirror from damage and stray light
Dovetail The massive PlaneWave dovetail supports the optical tube to provide rigidity. A matching dovetail clamp is available to install on various mounts.
Drawing (PDF)
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 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.

SHIPPING
Crated Shipping Weight 225 lbs (102.1 kg)
Crate Width 29 inch (737 mm)
Crate Height 33 inch (838 mm)
Crate Length 45 inch (1,143 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

Wrench Set (5812A35) English Hex Wrenches

£1,135.00

Planewave 0.66x Reducer for CDK 12.5

This is a reducer designed specifically for flat field telescopes like the CDK. This reduces the f ratio of the CDK telescope 66%. The CDK12.5 f/8 telescope will be reduced down to f/5.3.

Click here for Reducer Instruction Sheet

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Planewave CDK 20 Optical Tube

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.

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: Three cooling fan blow out of the optical tube pulling air though the telescope and pass the primary mirror. This helps the telescope to reach thermal equilibrium quickly. The fans are conrolled by a computer if the optional Electronic Focus Accessory (EFA Kit) is purchased.

Technical Specs:

OPTICAL 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 Racked in Focuser: 5.8 inch (147 mm)

Weight: 140 lbs (63.5 kg)
OTA Length: 47 inch (1,194 mm)
Upper Cage: Carbon Fiber Truss
Lower Cage: Carbon Fiber Truss with Carbon Fiber Light Shroud:
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%

SECONDARY MIRROR:
Diameter: 7.5 inch (191mm)
Material: Precision Annealed Borosilicate
Shape: Spherical
Coating: Enhanced Aluminum - 96%

LENS GROUP
Diameter: 90 mm (3.54 inch)
Number of lenses: 2
Coating: Broadband AR Coatings (less than .5% reflected from 400 to 700nm)

Crated Shipping Weight: 291 lbs (132.0 kg)
Crate Width:32 inch (813 mm)
Crate Height:36 inch (914 mm)
Crate Length:59 inch (1,499 mm)INCLUDED

ACCESSORIES
Ronchi Spacer: (200354) This spacer sits in place of a focuser and is used for setting the primary to secondary spacing. It has an 1 .25” inner diameter and may be used with 1.25” 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
Wrench Set

£1,135.00

Planewave 0.66x Reducer for 17 Inch CDK

This is a reducer designed specifically for flat field telescopes like the CDK. This reduces the f ratio of the CDK telescope 66%. The f/6.8 CDK17 and CDK20 telescopes will be reduced to about f/4.5.

Click here for reducer instruction sheet

Planewave Accessories

Accessories for the CDK 12.5 and 17 Telescopes