Pocket-Sized Wonder: DIY 3D-Printed Telescope Achieves Usable Performance
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A remarkably compact, fully functional Dobsonian telescope, small enough to fit in a jacket pocket, has been designed and meticulously tested by developer Lucas Sifoni, demonstrating the power of 3D printing and innovative design in amateur astronomy.
Lucas Sifoni’s project, documented beginning November 18, 2025, showcases a telescope built around a 76 mm mirror, prioritizing portability without sacrificing optical functionality. The design utilizes readily available materials and 3D-printed components, offering a compelling alternative to commercially produced telescopes for hobbyists and those interested in DIY projects.
Engineering a Telescope for Extreme Portability
The core challenge of this project was minimizing size. According to the project documentation, the telescope was engineered to comfortably fit inside an inner jacket pocket – a feat accomplished despite the need for structural support, provided by carbon rods. The telescope’s structure is almost entirely 3D-printed, leveraging the rigidity of PETG carbon-fiber filament to maintain a low overall weight.
The optical system features a 76 mm parabolic mirror with a 300 mm focal length, resulting in a fast f/4 ratio. This design choice balances image brightness with manageable optical aberrations. The mechanical design adheres to classic Dobsonian principles, emphasizing simplicity, smooth movement, and balance.
Improvised Mechanics and Clever Design Solutions
The telescope’s altitude and azimuth motions – controlling vertical and horizontal movement – rely on resourceful adaptations. The builder utilized improvised Teflon-style pads crafted from UHMW or HDPE furniture feet, paired with rubber backing, to achieve smooth tracking. Collimation, the precise alignment of the mirrors, is managed with nylon screws, while magnets securely hold the secondary mirror in position.
Focusing is achieved through a friction-based eyepiece holder, eliminating the need for complex hardware. The eyepiece slides within a printed tube, held in place by the natural flexion of the plastic. A Lycra shroud further enhances performance by blocking stray light and mitigating dew formation on the mirrors.
Optical Testing and Performance Evaluation
Rigorous optical testing, including interferograms and star tests, was conducted both before and after refiguring the primary mirror. Initial tests revealed the mirror was significantly overcorrected, a common issue with inexpensive spherical mirrors. However, after refiguring, Sifoni reported improved star symmetry and a Strehl ratio of approximately 0.9 – representing 90% of the theoretical maximum sharpness achievable by a perfect mirror of the same size. While the small mirror size inherently limits resolution, the results demonstrate a surprisingly high level of optical quality.
The project’s documentation explicitly states that this telescope isn’t intended to compete with larger, professional-grade instruments. However, it demonstrably succeeds as a genuinely usable optical device at an exceptionally small scale. The 3D files, assembly notes, and optical test results are publicly available, encouraging replication and modification by other enthusiasts.
The Celestron Travel Scope 80 Portable Refractor Telescope is available for purchase on Amazon.
The project exemplifies the growing accessibility of astronomy through DIY technology and open-source design. It proves that with ingenuity and modern tools like 3D printing, a functional and enjoyable astronomical experience can be achieved even within the constraints of extreme portability.
Anubhav Sharma, December 13, 2025 (Update: December 13, 2025)
