20 inch Ritchey-Chrétien Optical Tube Assembly

Part#: 200125

Price: $46,000.00

The PlaneWave Instruments PW20-RC is a 20 inch (0.51 m) f/6.8  Ritchey-Chrétien (RC) Astrograph telescope. The PW20-RC has a dual carbon-fiber truss design, with 3 cooling fans ejecting air from the back of the telescope.  The instrument weight is 140 lbs (64 kg) and comes standard with a back plate retaining ring ready to accept the focuser of your choice.

Also available with the CDK (Corrected Dall-Kirkham) optical design
   New Fused Silica mirror option available on all  CDK and RC models     200125Q - PW20-RC Fused Silica - $50,500

 

PlaneWave Instruments is pleased to offer the PW20-RC, a 20 inch (0.51 m) telescope with Ritchey-Chrétien optics. PlaneWave's CDK astrographs have become the telescopes of choice for universities, industry, and astrophotographers around the world, and now PlaneWave offers the PW-RC series to meet the custom needs of the scientific community.

The PW20-RC in its native format (no field flattening lenses) uses only a primary and secondary mirror with reflective coatings. This can be useful when making observations primarily on-axis and wide field imaging is not a concern.

Features:

Ritchey-Chrétien (RC) Optics RC optics made by PlaneWave for excellent on-axis performance using only a hyperbolic primary and secondary mirror with no refractive optics in the light path. (An optional field correcting lens group can be added to improve off-axis performance.)  
Carbon Fiber Truss Design Minimizes thermal expansion to prevent focus shift with changes in temperature
Dovetail expansion joint Accommodates the difference in thermal expansion between carbon fiber and aluminum. The expansion joint allows the aluminum dovetail to expand and contract without stressing the carbon fiber lower truss  
Cooling Fans Three cooling fan blow out the back of the optical tube, pulling air though the telescope and past the primary mirror. This helps the telescope to reach thermal equilibrium quickly. The fans are controlled by a computer if the optional Electronic Focus Accessory (EFA Kit) is purchased.  

OPTICAL SYSTEM

Optical Design Ritchey-Chrétien (RC)
Aperture 20 inch (508 mm)
Focal Length 3454 mm (135.98 inch)
Focal ratio F/6.8
Central Obstruction 39% of the Primary Mirror Diameter
Back Focus from Racked in Focuser 5.8 inch (147 mm)
Weight 140 lbs (63.5 kg)
OTA Length 47 inch (1,194 mm)
Upper Cage Carbon Fiber Truss
Lower Cage Carbon Fiber Truss with Carbon Fiber Light Shroud

SECONDARY MIRROR

Diameter 7.5 inch (191mm)
Material Precision Annealed Borosilicate
Shape Hyperbolic
Coating Broadband AR Coatings (less than .5% reflected from 400 to 700nm)

PRIMARY MIRROR

Optical Diameter 20 inch (508 mm)
Outer Diameter 20.5 inch (521 mm)
Shape Hyperbolic
Material Precision Annealed Borosilicate or Fused Silica
Coating Enhanced Aluminum - 96%


STANDARD FEATURES
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
Crated Shipping Weight 291 lbs   (132.0 kg)
Crate Width 32 inch   (813 mm)
Crate Height 36 inch   (914 mm)
Crate Length 59 inch   (1,499 mm)
INCLUDED ACCESSORIES
Ronchi Spacer (200354) This spacer sits in place of a focuser and is used for setting the primary to secondary spacing. It has an 1.25”  inner diameter and may be used with 1.25” oculars for collimation.
Ronchi Ocular This ocular is a Ronchi screen used for setting the primary to secondary spacing.
Primary Mirror Cover  The Primary Mirror Cover protects the primary mirror.
Printed Instructions  For Collimation and Spacing
12VDC Power Supply (18778)  Provides power for the fans (Not included for European Orders)
Wrench Set (5812A35 )  English Hex Wrenches (European Orders Only)
Camera Adapters Diagrams
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