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AG Optical - 20" Dall Kirkham Astrograph Telescope


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Manufactured by: AG Optical Systems


20" AG Optical Astrograph


  • Optics figured and quality tested as a system
  • Fast F6.7 system designed and baffled to cover 16803 size chip
  • 6" to 8.5" of back focus to support almost any combination of imaging components (dependent upon focuser selected)
  • Excellent coma free, astigmatism free, flat field performance over 70 mm image circle
  • Highly robust, precise Optec TCF-S3i focuser is standard.  Optional FLI Atlas focuser.
  • Outstanding field illumination across big chip cameras.
  • Carbon fiber truss tube engineered to provide rigidity and thermal stability.  Optional AGO Thermal Control System to automatically control fans, primary heater, and secondary heater.
  • Multiple spacer and camera adapter options


The 12" AG Optical astrograph has a medium focal ratio of f/6.7 and features an RMS spot size of 6 microns which makes for pinpoint images of stars at low field of views. This optical tube has a two element <0.5% reflective corrector which makes this possible by reducing many of the common light distortions such as coma. This RMS spot size can accomodate sensors as large as 16803. This 12" astrograph is also equipped with internal materials that help block and prevent stray light from affecting your images.

This AG Optical astrograph is equipped with the Optec TCF-S3i focuser. This focuser is beneficial not only because it is electronic and mechanical, it also allows focuser memory and very flexible backfocus of 6" which is perfect or many astrophotography combinations. If you want even more, there are many spacers and adapters available you can shoose from.


20" Optical Tube


  • AG Optical has equipped this astrograph with a carbon fiber tube, which is praised for its lightweight and thermal stability.



  • Cleaning and maintaining a telescope is standard. Dust, particles and moisture can infiltrate inside so it is important to clean your optics and instrument once and a while. With precise computer precision, AG Optical has designed their astrograph to be completely disassembled and reassembled without worrying about spacing differences between the internal optics. The aluminum components are also computer machined precisioned.


  • There are three 12 voltage speed variant fans behind the mirror that regulates temperature stability.







Additional Information

Name AG Optical - 20" Dall Kirkham Astrograph Telescope
Manufacturer AG Optical Systems
Model 20IDK
Aperture 20"
Backfocus Distance 6" with Optec TCF 8.5" with FLI Atlas
Cooling 4 x 80 mm fans
Focal Length 134"
Focal Ratio 6.7
Focuser Optec TCF-S3i
Optical Coatings Enhanced Aluminum
Optical Tube Truss
Optical Tube Length 45"
Primary Mirror Supremax 33 substrate
Secondary Mirror Obstruction 9"