Eta Carina Nebula (NGC 3372) - by Colin Eldridge
Taken with CDK700 (0.7 meter) Telescope
FLI ProLine 16803 CameraLearn More
PlaneWave Instruments now brings a fully automated observatory class telescope to the market in the CDK700, a 0.7 meter, Alt-Az telescope system. We are combining the revolutionary optical system that founded PlaneWave Instruments with a brand new innovative alt/az mount technology that sets a new standard for small observatory telescopes.
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.
Rotating Tertiary Mirror - CDK700 includes an integrated rotator for the tertiary mirror with magnetic locks to position it precisely for either Nasmyth focus positions.
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: Our 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.
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.
More about our Optical Design
|Optical Design||Corrected Dall-Kirkham (CDK)|
|Aperture||700 mm (27.56 inch)|
|Focal Length||4638 mm|
|Central Obstruction||42% of the Primary Mirror Diameter|
|Back Focus||305 mm (12 inch) from Mounting Surface|
|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 Diagram|
|Optimal Field of View||70 mm (0.86 degrees)|
|Focus Position||Nasmyth Focus|
|Fully Baffled Field||60 mm|
|Image Scale||22 microns per arcsecond|
|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|
|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.|
|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)|
|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||Pyrex or Borosilicate Precision Annealed|
|Edge Thickness||2.25 inch|
|Radius of curvature||2961 mm|
|Optical Diameter||270 mm|
|Outer Diameter||280 mm|
|Cell||3 point RTV|
|Optical Major Diameter||152.4 mm|
Imaging telescopes or lenses:Planewave Instruments CDK-700
Imaging cameras:FLI PL-16803
Guiding telescopes or lenses:Planewave Instruments CDK-700
Software:Diffraction Limited Maxim DL
Filters:Astrodon Gen 2
Dates: Aug. 25, 2012
Locations: Rural Observatory
Integration: 3.1 hours
Avg. Moon age: 7.84 days
Avg. Moon phase: 54.84%
NGC 253, an LRGB image, total imaging time 3.1 hours. All subs 400 seconds, 6 each for RGB and 10 for Luminance .
The IRF90 is a large capacity Integrated Focuser and Rotator. The Focuser is capable of lifting 40 lbs (18 kg) with a range 30 mm (30000 microns). The Rotator has a 90mm aperture with a range of 365 degrees with hardstops to elliminate any chance of cord wrap.
The IRF90 is compatable with the CDK17, CDK20, CDK24, and the CDK700.
The IRF90 requires a standard Electronic Focuser Assembly (EFA), already installed on most telescopes.
Download PlaneWave Interface and ASCOM drivers form our Download Page.