Astronomy Specialist





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PlaneWave Instruments is pleased to offer the PW20-RC, a 20 inch (0.51 m) f/6.8 astrograph 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.

The PW20-RC has a dual carbon-fibre truss design, with 3 cooling fans ejecting air from the back of the telescope. The instrument weight is 64 kg and comes standard with a back plate retaining ring ready to accept the focuser of your choice.



  • Carbon fibre tube minimizes thermal expansion, which causes focus shift as temperature changes during an imaging session. Carbon fibre also reaches ambient temperatures quickly and is extremely lightweight and rigid to help ensure excellent imaging data is produced.
  • Dovetail Expansion Joint allows for the difference in thermal expansion between carbon fiber and aluminium. The expansion joint allows the aluminium dovetail to expand and contract without stressing the carbon fiber lower truss.
  • Fused silica 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.
  • Three cooling fans blow out of the optical tube pulling air through the telescope and by the primary mirror. This helps the telescope to reach thermal equilibrium quickly. The fans are controlled by a switch on the optical tube, or can be controlled by via PWI3 software.


Optical system

Aperture 20" (508 mm)
Focal length
3454 mm
Focal ratio
Central obstruction
39% of primary mirror diameter
Backfocus from racked in focuser
147 mm
OTA length
1194 mm
Carbon fibre truss and light shroud
Weight 63.5 kg

Primary mirror

Optical diameter
508 mm
Outer diameter 521 mm
Precision Annealed Borosilicate or Fused Silica
Enhanced aluminium - 96%


Secondary mirror

191 mm
Precision Annealed Borosilicate
Broadband AR Coatings (less than .5% reflected from 400 to 700nm)


  • PW20-RC OTA
  • OTA cover to protect primary mirror
  • Printed instructions for collimation and spacing
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