https://lucassifoni.info/blog/miniscope-tiny-telescope/ Lucas Sifoni The tiniest yet real telescope I've built astronomy Nov 18 2025 Previous post : Guest post @ AppSignal - Debugging in Elixir with Observer --------------------------------------------------------------------- [IMG_2285] A "relaxation" project, mostly drawn on planes to and from Norway this month, where I had to travel to setup a digital art installation in Kristiansand with friends from the digital art collective Lab212. It has been drawn with one major constraint: it must fit in the inner pocket of my jacket (well, one specific jacket), except for the rods. This is a 3D-printed dobsonian telescope built around a 76mm/300mm parabolic mirror kit. While there are plenty of mini-scope models on the internet, I wanted something that looked like a dobson that went a bit too hard through the clothes dryer, but without compromise on what matters: * Balance * Smooth movements * Rigidity * Collimatable * Focusable eyepiece holder * A minimum of style (entirely subjective) Hardware * PETG-CF filament * 4mm carbon rods * M3 screws and M3x4.5x4.5 heat-set inserts * A spring * Nylon screws to collimate both the primary and secondary mirrors * 4 magnets for the secondary * A bit of paraffin to lubricate the focuser * A lycra light shroud that also helps with delaying dew forming on the mirrors The focuser follows Analog Sky's recipe: the tube that receives the eyepiece is also the movement itself, with a rounded thread that prints extremely smoothly with very little play. No additional hardware needed - the eyepiece is self-held by the flexion of plastic fins. All the holes for the rods are straight, which forces them to arch, which "locks" the structure in place. The alt/az movements use "teflon pads" (actually gray HDPE or UHMW for furniture feet) with rubber backing, scalped and glued. Download the 3D files on Printables * Discussion on Astrosurf If you build it, the real trick for ease of mounting is to chamfer the carbon rods with a 1mm chamfer at both ends and seal it with CA glue. See the chamfer pic in the gallery. Pocket dobson scale comparison Miniscope view 1 Miniscope view 2 Miniscope view 3 Miniscope view 4 Miniscope view 5 Miniscope view 6 Miniscope view 7 Miniscope view 8 Miniscope view 9 Miniscope view 10 Miniscope view 10 Miniscope view 11 Miniscope view 12 Miniscope view 13 Miniscope view 14 Miniscope view 15 Miniscope view 16 Miniscope view 17 Miniscope view 18 Optical tests Sadly, the results aren't great. We were used to very good l/6 or better recent buys from Aliexpress, but this one is very overcorrected. It was very smooth, with a rather good edge at the foucault, but is overcorrected by 70%. With the eyepiece I selected, putting it at 30x power, this does not show too much, and it retains its "real telescope" status. But this mirror is so small that I will not refigure it - the realuminizing costs would outweigh the entire project. Edit dec. 12th The l/6 aliexpress mirrors mentioned were spherical. So, great starting points to figure them, but unusable as-is. I did not yet stumble on a great parabola at a low price, and this is to be expected. Edit as of dec. 11th : of course I did not resist re-figuring it. It now hovers around 0.9 strehl. The star test with the selected eyepiece shows nice symmetric defocused stars and I can now count individual spider web strands and distinguish the dew droplets it carries, on a nearby electrical pole, whereas I did not even see the spider web with the mirror as it was from the factory. I still need to do a proper "showable" Bath report with enough interferograms, my last test was 4 interferograms and carries a ton of noise. So it is great but I now have to get it coated, and working a mirror this small did raise a few challenges in handling it. All test pictures below are before refiguring Optical bench overview Bath interferometer setup Interferometry test view Test setup detail Interferogram 1 Interferogram 2 Interferogram 3 Interferogram 4 DFT analysis 1 DFT analysis 2 DFT analysis 3 Refiguring the mirror on a little pitch lap x Previously on that topic : * The best 3d printable 6"f5 (150/750) portable travel dobsonian telescope as of today astronomy * EleusisT's 3D printable DIY 1:10 crayford reducer / fine focus knob astronomy CAD * 2024 amateur optics / astronomy updates astronomy * A lightweight and easy to build 1.25" crayford focuser astronomy * Heavy modifications to the 200mm f/3.52 dob's upper cage. optics astronomy telescope 3d-printing 2022 - 2025 Lucas Sifoni / Turing-Express, 32490 Castillon-Saves, Gers Entreprise Individuelle -- SIREN 799 377 452 contact@turing-express.fr * links : * people * email * GPG public key * linkedin If you are invested in / benefit from Erlang or Elixir, please consider adhering to the Erlang Ecosystem Foundation, either as an individual or as a company.