As the debate rages on about the value of AI-generated art, [Chris Borge] printed his own version of another technology that’s been the subject of debate about what constitutes real art. Meet the camera lucida.

Developed in the early part of the nineteenth century by [William Hyde Wollaston], the camera lucida is a seemingly simple device. Using a prism or a mirror and piece of glass, it allows a person to see the world overlaid onto their drawing surface. This moves details like proportions and shading directly to the paper instead of requiring an intermediary step in the artist’s memory. Of course, nothing is a substitute for practice and skill. [Professor Pablo Garcia] relates a story in the video about how [Henry Fox Talbot] was unsatisfied with his drawings made using the device, and how this experience was instrumental in his later photographic experiments.

[Borge]’s own contribution to the camera lucida is a portable version that you can print yourself and assemble for about $20. Featuring a snazzy case that holds all the components nice and snug on laser cut felt, he wanted a version that could go in the field and not require a table. The case also acts as a stand for the camera to sit at an appropriate height so he can sketch landscapes in his lap while out and about.

Interested in more drawing-related hacks? How about this sand drawing bot or some Truly Terrible Dimensioned Drawings?

It shouldn’t be a surprise that the idea of a planetarium originated with an electrical engineer, [Oskar von Miller] from the Deutsches Museum in Munich. According to [Allison Marsh] in IEEE Spectrum, he thought about the invention in 1912 as a way to demonstrate astronomical principles to the general public. While it seems obvious today that you can project the night sky onto a dome, it was a novel thought in 1912. So novel that the Carl Zeiss company first told [von Miller] to take a hike. But they eventually reconsidered and built the first planetarium, the Model I.

The engineer for Zeiss was a mechanical engineer by the name of [Walther Bauersfeld]. He was familiar with mechanical devices — orreries — that tracked the motion of the stars and planets. The goal was to translate those movements into a moving projection of light.

The practical realization of the projector required two independent projection spheres. One projected the stars and moved as a unit. It also held a cage that moved differently with projectors for the planets. Other separate projectors handled things like the Milky Way. There were 180 stars and the orbit of Saturn, just as an example was over 11 meters in diameter.

Even the domed projection room required innovative design. All of this would be easy with modern computers, but doing it all with gears seems quite a task. World War I slowed progress, but the Deutsches Museum committee saw an early demonstration of the device in late 1923. They were impressed.

Of course, the planetarium went on to become a…well, a star of science museums. Of course, there were improvements over time. Today, there are more than 4,000 planetariums worldwide. While [von Miller] and the Zeiss company made the first modern planetarium, mechanical devices date back to the time of [Archimedes], although they weren’t optical. However, in 1229, Emperor Frederick II acquired a tent with holes in it representing stars that rotated to show the movement of heavenly bodies.

Want to build your own private planetarium? [Gabby] did. You might want to grab some magnets.

Compared to through-hole construction, inspecting SMD construction is a whole other game. Things you thought were small before are almost invisible now, and making sure solder got where it’s supposed to go can be a real chore. Add some ball grid array (BGA) chips into the mix, where the solder joints are not visible by design, and inspection is more a leap of faith than objective proof of results.

Unless, of course, you put the power of optics to work, as [Petteri Aimonen] does with this clever BGA inspection tool. It relies on a pair of tiny prisms to bounce light under one side of a BGA chip and back up the other. The prisms are made from thin sheets of acrylic; [Petteri] didn’t have any 1-mm acrylic sheet on hand, so he harvested material from a razor blade package. The edge of each piece was ground to a 45-degree angle and polished with successively finer grits until the surfaces were highly reflective. One prism was affixed to a small scrap of PCB with eleven SMD LEDs in a row, forming a light pipe that turns the light through 90 degrees. The light source is held along one edge of a BGA, shining light underneath to the other prism, bouncing light through the forest of solder balls and back toward the observer.

The results aren’t exactly crystal clear, which is understandable given the expedient nature of the materials and construction employed. But it’s certainly more than enough to see any gross problems lying below a BGA, like shorts or insufficiently melted solder. [Petteri] reports that flux can be a problem, too, as excess of the stuff can crystalize between pads under the BGA and obstruct the light. A little extra cleaning should help in such cases.

Haven’t tackled a BGA job yet? You might want to get up to speed on that.