This guy Les put together a piece of software to view/calibrate a spectrum[0]. He also has a YT channel[1] where he builds a couple RasPi spectrometers using pre-made spectroscopes that run $50-100, but the whole package is a lot more compact.

There are also a number of spectroscope enclosures on thingiverse, but it's always so hard to gauge if any of the projects are actually worth printing. The most dead-simple and cheap example I found used the same slit/CD plastic combo capped onto the ends of a paper towel tube.

Some other stuff[2,3,4]

https://github.com/leswright1977/PySpectrometer

https://www.youtube.com/watch?v=jAV7bnNrE-M

https://physicsopenlab.org/2021/06/19/absorption-spectroscop...

https://www.effemm2.de/spectragryph/about.html

https://en.wikipedia.org/wiki/Absorption_spectroscopy

Generally, Public Lab builds and 3d print plans are worth your time. Everything they list is well-considered and well-maintained. When the stodgy old magazine The Economist wrote a "Punk Science" article about DIY science, they actually got them include a cut-out page to build a spectrometer :)

https://publiclab.org/wiki/economist

Found this after looking into cheaper alternatives to yesterday's post on a DIY spectrometer with a raspberry pi [0].

Also interesting, and even cheaper, is a paper spectrometer which attaches to a phone camera by the same designer as this Lego one [1].

0: https://news.ycombinator.com/item?id=30027804

1: https://publiclab.org/wiki/papercraft-spectrometer

That DVD film part is neat

Beginners question but what is its purpose?

Diffraction grating (separates light by wavelength)