This PlaneWave observatory telescope system comprises
- PlaneWave CDK14 OTA
- PlaneWave L-350 direct drive alt-az mount
PlaneWave's CDK14 is a 14-inch (0.36 m) aperture f/7.2 telescope that is very well suited for astro-imaging as well as for visual use. The CDK14 telescope utilises the Corrected Dall-Kirkham (CDK) optical design, developed by Dave Rowe, that provides excellent imaging possibilities 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 making the CDK an innovative solution for unsurpassed astro-imaging quality at an affordable price.
At the image plane of the CDK14, will give you pinpoint stars from the centre to the corner of its 70mm field of view without any field curvature, off-axis coma, or astigmatism. The no-compromise optical design is unique in making the optical alignment forgiving and collimation very easy which guarantees the user the best possible performance from the telescope.
The CDK14 features a dual carbon-fibre truss design, with 3 cooling fans blowing air throughout the back of the telescope, The instrument weighs 22kg (48 lbs) and comes as standard with a back plate retaining ring ready to accept the focuser of your choice. The telescope comes with fused Silica optics as standard.
The PlaneWave L-350 mount: is an alt-azimuth, single-fork arm style mount that is capable of carrying a total payload of 45kg/100lbs and therefore can easily carry a PlaneWave CDK14 and accessories (e.g. CCD Camera etc). The mount uses a direct drive motor system with high resolution encoders on both the RA and DEC axes that results in zero backlash and periodic error. The mount can slew at speeds from 20 degrees to up to 50 degrees per second!
The mount combines versatility, simplicity and affordability by combining all the technology of PlaneWave's Observatory-class telescopes into a compact and stand-alone mount and is a breakthrough in mount design, specification and features for the price.
The CDK14 telescope is an open truss tube design for a rigid, but lightweight structure, and for quick thermal cooling. The truss tube utilises a carbon fibre frame which minimises thermal expansion that can cause focus shift with changes in temperature. The carbon fibre truss tube design also promotes quick thermal cooling.
The CDK's carbon fibre truss poles
To create the telescope's baffles, Planewave uses digital 3D printing technology. Their 3D printers add successive layers of material to construct a baffle system with precision. These internal stray light baffles minimise vignetting and maximise image contrast.
3D Printed Primary Baffle
To mount the CDK14 onto a mount, PlaneWave supplies the CDK with a dovetail bar. The CDK features a dovetail expansion joint that allows for the difference in thermal expansion between carbon fibre and aluminium. This expansion joint allows the aluminium dovetail expand and contract without stressing the carbon fibre lower truss.
Dovetail expansion joint
To help the primary mirror to cool, there are three cooling fans that blow air inside the back of the telescope. Furthermore, internal diverting fins circulate air flow behind the mirror for even cooling to help the telescope reach thermal equilibrium quickly. The fans are controlled by a computer if the optional Electronic Focus Accessory (EFA Kit) is purchased.
Cooling Fans at the rear of the CDK14
For 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.
CDK14 Internal dew heater pads
The Ritchey Chrétien (RC) optical design has long been "the standard" in high end imaging telescopes due to its use in many professional observatories. The RC is successful in eliminating many of the problems that plague many other optical designs, namely off-axis coma, however the RC design does nothing to eliminate the damaging effects of off-axis astigmatism and field curvature. The RC design is also very difficult, and therefore expensive, to manufacture and optically align.
Optical Design of the PlaneWave Corrected Dall-Kirkham (CDK)
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.
In the image above, on the left column, the diagram shows a diffraction simulation for 14" CDK optics on the optical axis, and with a distance of 13 and 35mm from the optical axis. The right column shows the calculated spot diagram with small squares being 9 microns wide. The diameter of a star at the edge of the flat field corresponds to the pixel size of current large-format CCD chips and the imaging quality of the optics is limited only by the seeing conditions and the quality of the tracking. The large field of view of 70mm diameter offers enough tolerance for CCD cameras with ever increasing-sized sensors.
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.
Below are a few images taken with a CDK14 to show how well they perform.
PlaneWave L Series AZ Direct Drive
The PlaneWave L-350 features Direct Drive motors and on-axis encoders on both the RA and DEC axes. This eliminates the need for gear-based mechanics, thereby eliminating backlash and periodic error. With the high-resolution encoders providing feedback for the direct drive motors, not only will the telescope track without periodic error and backlash, the mount will also counter wind gusts with precise servo feedback.
PlaneWave L Series mount with CDK mounted ready for high speed slewing for satellite tracking.
The L-series direct drive motors can move the telescope at speeds from 2 degrees and up to 50 degrees per second. This makes the mount ideal for tracking satellites or just minimising celestial target acquisition time.
Dual mounting for PlaneWave L-Series mounts
The PlaneWave 8"-wide dovetail mounting bracket holds telescopes onto the inside of L mounts fork arm. An additional dovetail clamp is available to allow the mounting of an extra supplementary telescope on the outside of the fork arm adding to the mount's versatility.
Azimuth horizontal balancing system
Adding extra accessories to a single-mounted telescope, or adding a second telescope can affect the overal balance of the whole telescope. The upper portion of the L mount can be moved horizontally for precise centre-of-gravity balancing whether the mount is in Alt-Az or Equatorial configuration.
Internal through the mount cabling
To keep cabling from e.g. CCD cameras, filter wheels etc, the L- series mounts feature interior "through-the-mount" cable routing via access panels in the fork arm and azimuth axis sections.
PlaneWave CDK700's at work
The PlaneWave alt-az L-Series uses the same proven technology as used in the well-respected CDK700 telescopes which are being used in Universities such as the UK's University of Central Lancashire Alson Observatory >>HERE<<.
||Corrected Dall-Kirkham (CDK)
||14 inch (356mm)
||2563mm (101 inch)
||23.5% by surface area; 48.5% by diameter
|Back Focus from Mounting Surface
||11.09 inch (282 mm)
||48 lbs (22 kg)
||35 inch (889 mm)
||3.1 micron RMS at 13mm off-axis; 6.0 micron RMS at 35mm off-axis - Spot Diagram
||Carbon Fiber Truss
||Carbon Fiber Truss and Light Shroud
|Optimal Field of View
||70mm Image Circle
||165 mm (6.5 inch)
||Precision Annealed Borosilicate
||Enhanced Aluminum - 96%
||14 inches (355.6)
||14.5 inches (468.3mm)
||Enhanced Aluminum - 96%
||95mm (3.7 inch)
|Number of lenses
||broadband AR Coatings (less than .5% reflected from 400 to 700nm)
||The Corrected Dall-Kirkham design yields a perfectly flat field free from off-axis astigmatism, coma and defocus.
|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
||Three cooling fans blow air inside the back of the telescope. This helps the telescope to reach thermal equilibrium quickly. The fans are controlled by a computer if the optional Electronic Focus Accessory (EFA Kit) is purchased.
||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.
||Alt-Azimuth / Equatorial Direct Drive Mount
||110 lbs (50 kg)
|Max. Load Capacity
||100 lbs (45 kg)
||0 to 90 degrees, Northern and Southern hemispheres
||Equipment cables can be wired through mount
||PlaneWave Interface dual axis telescope control
||PlaneWave Interface 4 (PWI4) Control Software with integrated PointXP mount modeling software
||Home position sensors are included allowing the mount can find its home position on power up.
||20 degrees per second (standard); 50 degrees per second (maximum), both axes
||Accepts 120 VAC. Supplied with 12VDC 15A Regulated Power Adapter
||Industrial grade brushless motor control system and built in electronics
|Motor - Azimuth and Altitude
||Direct Drive 3 Phase Axial-Flux Torque Motors
|Encoder - Azimuth and Altitude
||152mm disk built into the azimuth and altitude axes with stainless steel encoder on the circumference with reader yields 18,880,000 counts per revolution of the telescope. This translates to about 0.069 arcsecond resolution
||Approximately 20 ft-lbs continuous; 50 ft-lbs peak
||Industrial grade, off-the-shelf brushless motor drives for each axis with custom designed interface card
|Telescope Control Software
||PlaneWave Interface (PWI4). Incorporates PointXP mount modeling software by Dave Rowe All ASCOM compatible.
||<10 arcsecond RMS with PointXP Model
||< .3 arcsecond error over 5 minute period
|System Natural Frequency
||10 Hz or greater