Ritchey Chretien 700

300mm f/6 MDDK Astrograph
600mm - 1000mm mm f/5.6 ECDKs

Ritchey-Chretien telescopes are popular for astrophotography and professional observatories due to their relatively large corrected field and absence of coma. The tube assembly is semi-ruggedised and is of fail-safe construction. The mirror supports in instruments under 600 mm are high precision floatation cells with full edge supports, larger mirrors are supported with kinematic face and edge supports. The focuser is included as standard, this is achieved by moving the secondary mirror

Price (Excl.VAT)


Aperture (mm)700
Recommended mount typeAlt-Az (included)
Tube tubeTruss
Focal length (mm)4200
Tube length (operating)1750
OTA Weight (kg)N/A
Back focus250
Focal ratio F/6
Cooling fansPrimary and secondary mirror
AirflowLaminar flow & Rear
Mirror coatingsEnhanced Aluminium + SiO2 protective layer
FocuserIntegrated JTW Rhino
Clear aperture (mm)75
Tube constructionCarbon fiber & Aluminium
Truss constructionPre-loaded carbon fiber
Optical surface quality (Strehl, PTV)0.97, 1/10
Primary mirror substrateFused silica
Primary mirror cell27 point kinematic cell
Primary mirror edge support12 point kinematic
Primary baffleSkeletal baffles
Secondary mirror substrateSchott Supremax 33
Secondary mirror cell6 point floatation cell
Secondary baffleSkeletal baffles
BoltingA4 Stainless steel
Metal protectionDual
Surface treatmentAluminium – 20 micron hard-coat anodising
PaintExterior grade powdercoat (environmentally friendly)
Anti dew systemIncluded