PlaneWave CDK 14"
Hot Product 2014, awarded by Sky&Telescope
After the successful introduction of the CDK 12.5" and 17" Astrograph from PlaneWave for few years ago, the CDK 14" is now available in an aperture of 14"- which is much easier to finance than a CDK 17".
The abbreviation CDK stands for the optical system of the PlaneWave astrographs - a Dall Kirkham Cassegrain with a optical correction unit. The result is a CDK 14" which is free from off-axis coma and off-axis astigmatism, yielding a perfectly flat field all the way out to the edge of a 70mm image circle. More about the Optical Design (CDK).
The PlaneWave CDK 14 is available in various types of mirror material. Standard mirror material is borosilicate. The telescope is also available in fused silica optics.
Fused Silicia is a synthetic amorphous silica glass of the highest purity and one of the most transparent glasses made. The optical and thermal properties of fused silica are superior to other types of glass due to its purity. Its transmission and homogeneity exceed those of crystalline quartz without the problems of temperature instability inherent in the crystalline form. Fused Silica has a coefficient of thermal expansion six times lower than Borosilicate (Pyrex) glass, which means that as fused silica cools down, it preserves its shape to a high degree of accuracy. This translates into consistent optical performance and unchanging focus over temperature changes. With its high melting temperature ()~ 1.600 degree Celsius), a very low coefficient of thermal expansion and resistance to thermal shock, fused silica is the material of choice for professional observatories as well as various scientific applications.
Due to the relatively low weight of just under 22kg (telescope tube), the CDK14 can be used on medium-sized mountings - eg a 10 Micron GM 2000 or an Astrophysics GTO 1100.
At this point, we will show you a spot diagram, to convince you about the high image quality of the CDK14. On the left column, the diagram shows a diffraction simulation for 14" CDK optics on the optical axis, and with a distance of 13- or 35mm to the optical axis. And the right column shows the calculated spot diagram. The small squares in the diagram are 9 micrometer (0.009 mm) 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 larger chips - also for amateur astronomy.
Pictures taken by CDK14":
Aperture 14 inch (356 mm) Focal Length 2563 mm(101 inch) Focal ratio f/7.2 Central Obstruction 23.5% by surface area; 48.5% by diameter Back Focus from Mounting Surface 11.09 inch (282 mm) Weight 48 lbs (22 kg) OTA Length 35 inch (889 mm) Optical Performance 3.1 micron RMS at 13mm off-axis; 6.0 micron RMS at 35mm off-axis UpperCage Carbon Fiber Truss Lower Cage Carbon Fiber Truss and Light Shroud Optimal Field of View 70mm Image Circle
Diameter 14 inches (355.6) Material Precision Annealed Borosilicate Shape Spherical Coating Enhanced Aluminum - 96%
Optical Diameter 14 inches (355.6) Outer Diameter 14.5 inches (468.3mm) Shape Prolate Ellipsoid Material Precision Annealed Borosilicate or Fused Silica Coating Enhanced Aluminum - 96%
Diameter 95mm (3.7 inch) Number of lenses 2 Coating Broadband AR Coatings (less than .5% reflected from 400 to 700nm)
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 Cooling Fans 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. 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.
|Optical Design||Corrected Dall-Kirkham (CDK)|
|Back Focus Distance||11.09" (282 mm) from Mounting Surface|
|Aperture (mm)||14" (356 mm)|
|Focal Length||2.563 mm (101 inch)|
|Image Field||70 mm|
|Central Obstruction||23.5% by surface area, 48.5% of the Diameter|
|Optical tube length||35 inch (889 mm)|
|Optical Tube Weight Copy||48 lbs (22 kg)|