Dall-Kirkham Optical Tube Assembly 20”

Part#: 200120

Price: $35,000.00

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 four different apertures 24", 20", 17" and 12.5"


Aperture 20" (.51m)
Focal Length 3454 mm
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


Diameter 7.5"
Material Precision Annealed Pyrex
Shape Spherical
Coating Protected Gold Reflective Coating - 98% (.65-16micron)


Material Precision Annealed Pyrex


Material Precision Annealed Pyrex

Carbon Fiber Truss 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 fan blow out of the optical tube pulling air though the telescope and pass the primary mirror. This helps the telescope to reach thermal equilibrium quickly. The fans are conrolled by a computer if the optional Electronic Focus Accessory (EFA Kit) is purchased.
SHIPPING <table "> Crated Shipping Weight291 lbs   (132.0 kg)Crate Width32 inch   (813 mm)Crate Height36 inch   (914 mm)Crate Length59 inch   (1,499 mm)