Free STLs: Build a 3D-Printed Mini Mirror Telescope

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January 4, 2026 Applications 9718

Maker develops 3D-printed mini mirror telescope and provides 3D models free of charge

With the help of 3D printing, maker Lucas Sifoni shows how compact a reflector telescope can be designed without compromising on key mechanical functions. The project is based on a standard mirror kit with a diameter of 76 millimeters and a focal length of 300 millimeters. Two printed frames form the basic structure and are connected by 4-millimeter carbon rods. The eyepiece and mirror assembly are located in the front frame, the eyepiece is screwed in and also serves for focusing. An azimuth-elevation mount, which is also printed, enables alignment.

Unlike refractors, the design uses the classic principle of the reflecting telescope. A parabolic primary mirror focuses the light and directs it into the eyepiece via a secondary mirror. This design is considered relatively easy to implement and is well suited for compact constructions. Sifoni deliberately based his design on the Dobsonian construction, but placed emphasis on balance, smooth movements, rigidity, and a collimated and focusable eyepiece holder.

The components are printed from PETG-CF. Other hardware includes M3 screws, heat-set threaded inserts, a spring, and nylon screws for adjusting the primary and secondary mirrors. Four magnets secure the secondary mirror. A Lycra light shield reduces stray light and delays fogging on the mirrors. The focuser follows the Analog Sky approach. The eyepiece tube is also the moving element and runs in a rounded thread, which, according to the developer, can be printed with minimal play. Additional clamps are not required; plastic slats hold the eyepiece in place thanks to their elasticity. The project files are available free of charge as 3D models on Printables.