Infrared Dall-Kirkham Optical Tube Assembly
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This is a Dall-Kirkham optical design with coatings that are optimized to transmit in infrared 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. The 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. The IR DK is available in the three different apertures, 20\", 17\" and 12.5\"
Features and Specifications for IR DK20
System
| Aperture | 20\" (.51m) |
| Focal Length | 3454 mm |
| Focal ratio | f/7 |
| Central Obstruction | 39% of the Primary Mirror Diameter |
| Back Focus | 8.9\" from focuser mounting surface, 5.81\" from racked in focuser |
| Weight | 140 lbs |
| OTA Length | 47\" |
| Upper Cage | Carbon Fiber Truss |
| Lower Cage | Carbon Fiber Truss with Carbon Fiber light shroud |
| Dimensions | Overall Dimensions |
Primary Mirror
| Diameter | 20.5\" |
| Aperture | 20\" |
| Focal ratio | f/3 |
| Mounting | Laser Collimated and Permanently Fixed |
| Material | Precision Annealed Pyrex |
| Shape | Prolate Ellipsoid |
| Coating | Protected Gold Reflective Coating - 98% (.65-16micron) |
Secondary Mirror
| Diameter | 7.5\" |
| Material | Precision Annealed Pyrex |
| Shape | Spherical |
| Coating | Protected Gold Reflective Coating - 98% (.65-16micron) |
Standard Features
| Dual Carbon Fiber Truss Design | Minimizes thermal expansion which causes focus shift with changes in temperature |
| Carbon Fiber Lower Light Shroud | Protects the primary mirror from damage and from stray light |
| 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 |
| Dovetail | The CDK20 comes with one of two dovetail designs. The first is the massive PlaneWave dovetail and the second is a dovetail compatible with Software Bisque\'s Versa Plate, VP dovetail. Both utilize the expansion joint listed above. |
| 3.5” Hedrick Focuser | Heavy duty no-slip focuser. The focus tube runs on 5 bearings and is driven by a leadscrew so there is no chance of slipping. It accepts an optional dial indicator and PlaneWave’s EFA Kit to control many electronic accessories. The draw tube travel is 1.3\". (View picture) (View picture2) |
| Cooling Fans | Three fans blow out of the optical tube pulling air though the telescope and by the primary mirror. This helps the telescope to equilibrate quickly. The fans are controlled by a switch on the optical tube or can be controlled by a computer if the optional Electronic Focus Accessory (the EFA Kit) is purchased. |
Shipping Dimensions and Weight
Crate Dimensions: 59\" X 32\" X 36\"
Crate Shipping Weight: 291 lbs
IR DK17
![\"Image\"](\"image/catalog/product/cdk17_3_400px.jpg\" "\\"Image\\"")
Features and Specifications for IR DK17
System
| Aperture | 17\" |
| Focal Length | 2939 mm |
| Focal ratio | f/6.8 |
| Central Obstruction | 39% |
| Back Focus | 8.8\" from focuser mounting surface, 5.8\" from racked in focuser |
| Weight | 94 lbs |
| OTA Length | 37\" |
| Upper Cage | Carbon Fiber Truss |
| Lower Cage | Carbon Fiber Truss with Carbon Fiber light shroud |
| Overall Dimensions | Dimensions PDF |
Primary Mirror
| Diameter | 17.75\" |
| Aperture | 17\" |
| Focal ratio | f/2.6 |
| Mounting | Laser Collimated and Permanentely Fixed |
| Material | Precision Annealed Pyrex |
| Shape | Prolate Ellipsoid |
| Coating | Protected Gold Reflective Coating - 98% (.65-16micron) |
Secondary Mirror
| Diameter | 6.25\" |
| Material | Precision Annealed Pyrex |
| Shape | Spherical |
| Coating | Protected Gold Reflective Coating - 98% (.65-16micron) |
Standard Features
| Carbon Fiber Tube Design | Minimizes thermal expansion which causes focus shift with changes in temperature |
| Carbon Fiber Lower Light Shroud | Protects the primary mirror from damge and from stray light. |
| 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 |
| 3.5” Hedrick Focuser | Heavy duty no-slip focuser. The focus tube runs on 5 bearings and is driven by a leadscrew so there is no chance of slipping. It accepts an optional dial indicator and PlaneWave’s EFA Kit to control many electronic accessories. The draw tube travel is 1.3\". (View picture) (View picture 2) |
| Colling Fans | Three fans blow out of the optical tube pulling air though the telescope and by the primary mirror. This helps the telescope to equilibrate quickly. The fans are controlled by a switch on the optical tube or can be controlled by a computer if the optional Electronic Focus Accessory (the EFA Kit) is purchased. |
Shipping Dimensions and Weight
Crate Dimensions: 45\" x 29\" x 33\"
Crate Shipping Weight: 225 lbs
IR DK12.5
![\"Image\"](\"image/catalog/product/side_view1_400px.jpg\" "\\"Image\\"")
Features and Specifications for IR DK12.5
System
| Aperture | 12.5\" |
| Focal Length | 2541 mm |
| Focal ratio | f/8 |
| Central Obstruction | 39% |
| Back Focus | 10.445\" from focuser mounting surface, 7.2\" from racked in focuser |
| Weight | 46 lbs |
| OTA Length | 31\" |
| Optical Tube | Carbon Fiber |
| Optical Performance | Diffraction Limited across 20mm field from 8 to 12micron. Spot and Diffraction Diagrams |
| Overall Dimensions | Dimensions PDF |
Primary Mirror
| Diameter | 13\" |
| Aperture | 12.5\" |
| Focal ratio | f/8 |
| Mounting | Laser Collimated and Permanentely Fixed |
| Material | Precision Annealed Pyrex |
| Shape | Prolate Ellipsoid |
| Coating | Protected Gold Reflective Coating - 98% (.65-16micron) |
Secondary Mirror
| Diameter | 4.65\" |
| Material | Precision Annealed Pyrex |
| Shape | Spherical |
| Coating | Protected Gold Reflective Coating - 98% (.65-16micron) |
Standard Features
| 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 |
| 2.75” Hedrick Focuser | Heavy duty no-slip focuser. The focus tube runs on 5 bearings and is driven by a leadscrew so there is no chance of slipping. It accepts an optional dial indicator and PlaneWave’s EFA Kit to control many electronic accessories. The draw tube travel is 1.3\". (View picture) (View picture 2) |
| Cooling Fans | Three fans blow filtered air onto the back of the primary mirror to help it quickly equibrate to the ambient temperature. The fans are controlled by a switch on the optical tube or can be controlled by a computer if the optional EFA Kit is purchased. |
Shipping Dimensions and Weight
Crate Dimensions: 41\" x 23\" x 31\"
Crate Shipping Weight: 163 lbs
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