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20 inch Ritchey-Chrétien Optical Tube Assembly

SKU# 200125Q

Price: $50,000.00


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


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.



Optical System

Optical DesignRitchey-Chrétien (RC)
Aperture20 inch (508 mm)
Focal Length3454 mm (135.98 inch)
Focal ratioF/6.8
Central Obstruction39% of the Primary Mirror Diameter
Back Focus from Racked in Focuser5.8 inch (147 mm)
Weight140 lbs (63.5 kg)
OTA Length47 inch (1,194 mm)
Upper CageCarbon Fiber Truss
Lower CageCarbon Fiber Truss with Carbon Fiber Light Shroud

Secondary Mirror

Diameter7.5 inch (191mm)
MaterialPrecision Annealed Borosilicate
CoatingBroadband AR Coatings (less than .5% reflected from 400 to 700nm)

Primary Mirror

Optical Diameter20 inch (508 mm)
Outer Diameter20.5 inch (521 mm)
MaterialPrecision Annealed Borosilicate or Fused Silica
CoatingEnhanced Aluminum – 96%


Crated Shipping Weight291 lbs   (132.0 kg)
Crate Width32 inch   (813 mm)
Crate Height36 inch   (914 mm)
Crate Length59 inch   (1,499 mm)

Included Accessories

Primary Mirror CoverThe Primary Mirror Cover protects the primary mirror.
Printed InstructionsFor 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)

For warranty information please check our Standard Warranty Page