A wall-mounted display made from 18 golden hexagonal mirrors

Peer Into Space Through This James Webb-Style Hexagonal Mirror

July 17, 2022 by Robin Kearey 2 Comments

The James Webb Space Telescope (JWST) generated considerable excitement when its first test images were released earlier this year: they proved that the instrument was working and helped its engineers to set up all systems for maximum performance. But the real proof of the pudding came last week, when the first batch of beautiful full-scale pictures was unveiled. If you thought those pictures were pretty enough to hang on your wall, you’re not the only one: [Fredrik], also known as [Cellar Nerd], built a wall-mounted display, shaped like the JWST’s main mirror, that cycles through images taken by the space telescope.

The frame holding the mirror is made of plywood. [Fredrik] designed it in Fusion 360, but decided to cut it by hand using a jigsaw; 3D printing the thing would have resulted in a large number of small pieces that might be hard to fit together with sufficient accuracy. After cutting the wood and painting it black, it was simply a matter of sticking the mirror tiles on top and the basic JWST design was done.

The set of eighteen golden hexagonal mirrors might seem to be the hardest bit to make, but was actually the easiest: [Fredrik] simply bought them ready-made on Amazon. The item’s description didn’t include any precise measurements, so he had to wait until the mirrors arrived before he could make the rest of the setup. The segments also don’t have the nanometer accuracy required for a real telescope: in fact, they’re not even flat enough to be useful as an everyday mirror. But that doesn’t really matter: the whole setup is pretty enough that [Fredrik]’s wife even wanted it to have pride of place in the hallway.

An old 15.6″ laptop display sits behind the frame and shows an image through the gap in the center. The display is quite a bit larger than necessary, so the images are always placed in the middle of the screen and scaled to obtain the correct size. A Raspberry Pi 2 is used to store the images and drive the display; it currently cycles through a fixed set of pictures, but [Fredrik] plans to have it automatically download the latest JWST images once a reliable online source is available.

If the basic design looks a bit familiar, you might have seen this static James Webb mirror that we featured before. We’ve also taken a deep dive into the fascinating engineering behind the JWST’s cryocooling system that gives it its spectacular infrared performance. Continue reading “Peer Into Space Through This James Webb-Style Hexagonal Mirror” →

Hexagonal Mirror Array Hides Hidden Message

November 14, 2021 by Donald Papp 18 Comments

[Ben Bartlett] recently got engaged, and the proposal had a unique bit of help in the form of a 3D-printed hexagonal mirror array, whose mirrors are angled just right to spell out a message with the reflections. A small test is shown above projecting a heart, but the real deal was a bigger version reflecting the message “MARRY ME?” into sand at sunset. Who could say no to something like that? Luckily for all of us, [Ben] shared all the details of what went into designing and building such a thoughtful and fascinating device.

Mirrors on the 3D-printed array are angled just right to reflect light into a message.

Essentially, the array of mirrors works a bit like a projector. Each individual reflection can be can be thought of as a pixel, and the projected position of each can be modified by the precise angle of each mirror. With the help of some Python code, [Ben] calculated the exact angles needed to spell out “MARRY ME?” and generated the necessary 3D model. A smaller-scale test (shown in the header image above) was successful, and after that it was just a matter of printing the array and gluing on some mirrors.

Of course, that’s the short version. In practice there were quite a few troublesome issues that demonstrated the value of using early tests to discover hidden problems. For one thing, mirror angle and alignment is crucial, which meant that anything that could affect the shape of the array was a potential problem. Glue that expands or otherwise changes shape as it dries or cures could slightly change a mirror’s angle, so cyanoacrylate (CA) glue was preferred. However, the tiniest bit of CA glue will mess up a mirror’s surface in a hurry, so care was needed during assembly.

The gleaming hexagonal mirrors are reminiscent of the James Webb Space Telescope.

Another gotcha was when [Ben] suddenly realized, twenty hours into printing the final assembly, that the message needed to be reversed! As designed, the array he was printing would project “?EM YRRAM” and this wasn’t caught during testing because the test pattern (a heart) was symmetrical. Fortunately there was time to correct the error and start again, but it was close. [Ben]’s code has an optional visualization function, which was invaluable for verifying that things would actually turn out as expected. As it happens, the project took right up to the last minute to complete and there wasn’t quite time to check everything 100% before the big moment, but it all turned out alright. What’s life without a little mystery and danger, anyway?

The pictures are great, but you won’t regret taking the time to read through the project page (don’t miss the annotated Python code) because [Ben] goes into just the right level of detail. The end result looks fantastic, and makes an excellent keepsake with a charming story.