PlaneWave CDK700 Alt-Az Telescope

PlaneWave CDK700 Alt-Az Telescope

PlaneWave CDK700

PlaneWave Instruments brings a fully automated observatory class telescope to the market in the CDK700, a 0.7 meter, Alt-Az telescope system. The CDK700 combines the revolutionary optical system that founded PlaneWave Instruments with an innovative Alt-Az mount technology that sets a new standard for small observatory telescopes.

CDK700 Features

An alt/az mount is inherently more stable than an equatorial mount as there is no cantilevered mass, nor are there any large counterweight protruding that are very dangerous in a public observatory. The mass it takes to make a rigid Alt/Az mount is substantially leading to cost savings. There is no dealing with balance changes as you cross the meridian or meridian flips that German Equatorial Mounts have to deal with. You can image from horizon to horizon continuously if desired. Alt/Az is more intuitive to use and there is no polar alignment needed. Besides, it is the way the big boys do it.

Benefits of Nasmyth Focus

The Nasmyth Focus is along the altitude axis so there are virtually no balancing issue as you change out equipment. In addition the CDK700 comes standard with a field rotator / field framer.

Direct drive motors and encoders

Direct Drive motors means that there are no gears which cause backlash and periodic error. With the high resolution encoders providing the feedback for the direct drive motors, not only will the telescope track without periodic error or have any backlash at all, but the mount will be able to counter against wind gusts. The direct drive motors can move the telescope at incredible speeds for tracking satellites or just to minimize target acquisition time.

CDK Optical Design

The PlaneWave design produces a flat, coma free and astigmatic free field of view. Since the secondary mirror is spherical, centering is very forgiving, which means it is easy to get the telescope optics aligned for optimum performance, this is not the case for most high-end astrographs. The end result at the image plane of the CDK design is no off-axis coma, no off-axis astigmatism, and a perfectly flat field, all the way out to the edge of a 50mm image circle. All this means, the stars will be pinpoints from the center of the field of view out to the corner of the field of view.

Ritchey-Chr├ętien Optics Option: In certain applications such as photometry and spectroscopy, refractive lenses could influence scientific results. The PW700-RC in its native format (no field flattening lenses) uses only a primary and secondary mirror with reflective coatings. This can be useful when making observations primarily on-axis and wide field imaging is not a concern.

Cost: Adds $25,000 to the base price.


Starting at $210,000
Corrected Dall-Kirkham / Ritchey-Chr├ętien Optics Comparison
PlaneWave CDK700 Brochure
PlaneWave Videos

Optical Specifications

Optical Design: Corrected Dall-Kirkham (CDK)

Aperture: 700 mm (27.56 inch)

Focal Length: 4638 mm

Focal ratio: f/6.6

Central Obstruction: 42% of the Primary Mirror Diameter

Back Focus: 305 mm (12 inch) from Mounting Surface

Weight: 1,200 lbs

Optical Tube: Dual truss structure with Nasmyth focus

Optical Performance: 1.8 micron RMS spots [25mm on-axis] (400 to 900nm) 4.4 micron RMS spots [21mm off-axis] (400 to 900nm) 6.8 micron RMS spots [35mm off-axis] (400 to 900nm) (Spot and Diffraction Diagrams)

Usable Field of View: 70 mm (0.86 degrees)

Focus Position: Nasmyth Focus

Fully Baffled Field: 60 mm

Image Scale: 22 microns per arcsecond

Mechanical Specs

Fork Assembly: Single piece U shaped fork arm assembly for maximum stiffness

Azimuth Bearing: 20 inch diameter thrust bearing

Altitude Bearing: 2 x 8.5 inch OD ball bearings

Optical Tube: Dual truss structure with Nasmyth focus

Motion Control

Motor Control: Industrial grade Parker brushless motor control system and built in electronics

Azimuth Motor: Direct Drive 3 Phase Axial-Flux Torque Motor

Altitude Motor: Direct Drive 3 Phase Axial-Flux Torque Motor

Encoder - Azimuth and Altitude: 10 inch disk built into the azimuth and altitude axes with stainless steel encoder tape on the circumference with reader yields 16 million counts per revolution of the telescope. This translates to about 0.08 arcsecond resolution.

Motor Torque: Approximately 35 ft-lbs

Drive Electronics: Capable of controlling up to 4 high speed encoders, limit switch inputs, homing switch inputs, controls two additional motors for accessories, two brake outputs and 16 digital and 2 analog inputs

Telescope Control Software: Incorporates PointXP mount modeling software by Dave Rowe. All ASCOM compatible.

Primary Mirror Blank Spec

Radius of Curvature: 4115mm

Optical Diameter: 700 mm (27.56 inch)

Outer Diameter: 714.38 mm (28.125 inch)

Core Diameter: 203mm (8 inch)

Material: Fused Silica

Edge Thickness: 2.25 inch

Cell: 18 point

Secondary Mirror Blank Spec

Radius of curvature: 2961 mm

Material: Fused Silica

Thickness: 25 mm

Optical Diameter: 270 mm

Outer Diameter: 280 mm

Cell: 3 point RTV

Third Mirror Blank Spec

Optical Major Diameter: 152.4 mm

Material: Fused Silica

Thickness: 25 mm

System Performance

Pointing Accuracy: 10 arcsecond RMS with PointXP Model

Pointing Precision: 2 arcsecond

Tracking Accuracy: 1 arcsecond error over 3 minute period

System Natural Frequency: 10 Hz or greater

Field De-Rotator Accuracy: 3 microns of peak to peak error at 35mm off-axis over 1 hour of tracking (18 arc sec)