PlaneWave IRDK700 Dall-Kirkham f/6.5 (various versions available)

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PlaneWave IRDK700 Dall-Kirkham f/6.5 (various versions available)
  • IRDK7700 Nasmyth Astrograph, 28 inch Infrared optimized with Borosilicate Optics or Fused Silica Optics
  • inkl. IR90 Derotator und Fokuser for up to 18 kg
    instrument weight
  • focal length 4638mm (f/ 6.6), with a 70mm image circle
  • rotatable tertiary mirror with positioning device
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Description

Details

PlaneWave IRDK 700 - 28" Astrograph der professionellen Universitätsklasse

Planewave Dall-Kirkham Optical Tube Assembly
CDK 700

The IRDK700, a 0.7 meter, is a fully automated observatory class telescope and direct drive alt-azimuth mounting system designed and engineered by PlaneWave.

This is a Dall-Kirkham optical design with coatings that are optimized to transmit in infrared or ultra violet wavelengths. It is diffraction limited across a 20mm image circle at the focal plane. There are no refractive lens, only reflective components to the design. For IR application, reflectives coatings are a protected gold which give better than 98% reflectivity from .65 micron (650nm) to 5 micron (5000nm). This design is ideal for infrared astronomy or LIDAR applications. UV optimized coatings can also be used at an additional cost.

The DK is available in the three different apertures 12.5 ", 20", 24" and 28".

The PlaneWave IRDK700 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.

Freatures

  • Pinpoint stars out to a 70mm image circle
  • Direct-drive motors on each axis for smooth, fast, and virtually silent movement of the telescope. Direct Drive motors mean that there are no gears to cause backlash and periodic error
  • High resolution encoders on each axis for precise positioning
  • Incorporates PointXP mount modeling software by Dave Rowe All ASCOM compatible.
  • Dual Nasmyth focus, allowing simultaneous mounting of two instruments or easy switching between visual and imaging use
  • integrated rotator for the tertiary mirror, with magnetic locks to position the mirror precisely for either Nasmyth focus position. The rotator can move from one port to the other in under 10 seconds.
  • Field de-rotator / rotational field framing

Benefits of Nasmyth Focus: The Nasmyth Focus is along the altitude axis so there are virtually no balancing issue as you change out equipment. Eyepieces remain at a constant wheelchair-accessible height, greatly simplifying access to the telescope for public observatories. The rotating tertiary mirror allows you to switch from one Nasmyth port to the other in just seconds, allowing observers to easily transition between imaging and visual use

Specifications:

OPTICAL SYSTEM

Aperture 27.56 inch (700 mm)
Focal Length 4540 mm
Focal ratio 6.5
Central Obstruction 47% of the Primary Mirror Diameter
Back Focus from Mounting Surface 309 mm (12.2 inch)
Weight 1,200 lbs(544 kg)
OTA 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)
Dimensions 93.73" H x 43.25" W x 39" D
Focus Position Nasmyth Focus
Fully Baffled Field 60 mm
Image Scale 22 microns per arcsecond
Optimal Field of View 70 mm (0.86 degrees)

 

MECHANICAL STRUCTURE

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 30 ft-lbs continuous; 60 ft-lbs peak
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.

 

SYSTEM PERFORMANCE

Pointing Accuracy 10 arcsecond RMS with PointXP Model
Pointing Precision 2 arcsecond
Tracking Accuracy  
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)

 

PRIMARY MIRROR

tr>Cell18 point

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

 

SECONDARY MIRROR

Radius of Curvature 2961 mm
Optical Diameter 312.4 mm (12.3 inch)
Outer Diameter 317.5 mm (12.5 inch)
Core Diameter 203mm (8 inch)
Material Fused Silica
Thickness 25 mm
Cell 3 point RTV

 

TERTIARY MIRROR

Optical Major Diameter 152.4 mm
Material Fused Silica
Thickness 25 mm
Specifications

Additional Information

Manufacturer Planewave
SKU (#) pw-IRDK700
Back Focus Distance 12.2" (309 mm) from Mounting Surface
Aperture (mm) 27.56" (700 mm)
Focal Length 4.540 mm (175.74 inch)
Image Field 70 mm
Central Obstruction 47% of the Primary Mirror Diameter
Substrate Borosilicate,Fused Silica
Focal Length f/6.5
Optical Tube Dall-Kirkham
Weight (lbs) 1200 lbs (544 kg)
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