The Planewave Instruments 20-inch (0.5-meter) f/6.8 corrected Dall-Kirkham telescope at Moore Observatory in Kentucky and its identical companion at Mt. Kent Observatory in Queensland, Australia, are a unique optical design that provides a wide, extremely well-corrected, field ideal for CCD imaging and photometry.

The CDK20 North at Moore Observatory has been our primary platform for developing technology for remote and robotic operation in the Shared Skies program. The Planewave Ascension 200HR mounting seen in the photo features direct axis encoders for arcsecond positioning, and enables unguided long exposure imaging and precision photometry with both northern and southern telescopes.

The corrected Dall-Kirkham design has an ellipsoidal primary, spherical secondary, and doublet corrector. It maintains a fixed primary-secondary spacing to minimize aberrations, and focuses by moving the camera into the focal plane. The Hedrick focuser on this telescope has a motor driven encoded screw drive and is exceptionally stable. With its carbon composite truss and engineering to avoid thermal stresses, the telescope reliably maintains focus night after night within seeing tolerance unless there is a very large temperature swing. The focal scale of arcseconds per millimeter provides a 37x37 arcminute field of view with the Apogee 16M camera that is its primary detector. An Optec IFW3 filter wheel in the optical train provides a selection of Sloan filter set (g', r', z', i') filters which are used both for photometry and for RGB imaging. Narrowband filters for selected emission lines from nebulae and stellar chromospheres are also provided on alternative filter wheels.

Instrumentation available for remote operation of the CDK20 North telescope includes

• Apogee 16M 4096x4096 (16 megapixel) 0.54" pixels with 37' field
• g'r'z'i' filter wheel
• H-alpha, H-beta, [O III], He I, Na D narrow band filter wheel
• Encoded focuser
• Axis quad video server to send realtime video to the remote observer
• Watec (Stellacam III) and Colorado Video frame integrator field of view on the video server
• Telescope monitor camera in the dome also on the video server
• Fisheye 180 degree view of the sky with a Watec integrating video camera and network interface
• Network controlled power switching
• RFID tag encoded dome rotation with autotracking software
• Remotely operable upper and lower dome shutter
• Remote sensing of weather, clouds, rain, and dew

The CDK20 North photo gallery has more views of the dome and telescope. Images taken with the CDK telescopes which demonstrate their exceptional resolution and wide field are available in the Shared Skies Gallery.