CANON_EF is a 3D astronomy project designed to enable the 3D printing of two adapters that connect Canon EF lenses to astrophotography cameras equipped with M42 (T2) or M48 threads.
This project provides a practical solution for attaching Canon EF lenses to astronomy cameras while preserving the required optical spacing between the lens and the camera sensor.
- Lens connector: adapts a Canon EF lens mount.
- Camera connector: available in M42 (T2) and M48 versions for compatibility with astrophotography cameras.
- Mount bracket: allows the assembled adapter to be attached to an astronomical mount.
The two main adapter parts are designed to maintain the correct distance of 44 mm between the lens and the camera sensor. This is required for cameras with a back focus of 12.5 mm.
This setup is intended for astrophotography applications where Canon EF lenses are used with cameras that require specific adapter spacing and thread compatibility.
Recommended slicing parameters:
- Lens connector and M42/M48 connectors: 0.2 mm layer height, 3 to 4 walls, 25% to 30% infill.
- Mount bracket: 0.3 mm layer height, 3 to 4 walls, 30% to 40% infill.
Illustration of the three-element mounting setup:
 Assembly M42 |
 Assembly M48 |
The repository contains the main FreeCAD project file and the associated STEP files for the different connector and bracket components:
- lens-camera-adapters.FCStd — FreeCAD project file
- Canon_EF-Lens_connector.step — Canon EF lens connector
- Canon_EF-M48_connector.step — M48 camera connector
- Canon_EF-T2_connector.step — T2/M42 camera connector
- Canon_EF-Mount_bracket.step — astronomical mount bracket
These parts are assembled mainly by friction and mechanical fit. They are best suited for small astrophotography setups, such as compact lenses like the Sigma 17-70 mm and small planetary cameras such as the ZWO ASI224 or Player One Mars C II.
If a heavier camera is used, the system should be mechanically secured with a locking screw for the camera to prevent accidental slackening or detachment.