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I occasionally wish I had a spectrometer, and last week was one of those occasions. Since I tend to make more of my own equipment than I should, before I knew it I was googling for “make cheap spectrometer.” The search turned up a fantastic page with instructions and pictures which inspired me to hack up something similar. I figured you could make something with a CD as a diffraction grating, but didn’t realize it was possible to get such high-quality images. Particularly the fact that you can make out the Fraunhofer lines means that it’s easy to make precise measurements by using the lines for callibration.

Here are a two pics, the first taken with my Casio EX-Z750, the second with an older Sony DSC-P5.

It’s interesting that the two cameras produce very different colors for the same spectrum. The Sony is far better in this case, but still not so good. Unless my eyesight is going, I don’t see much violet, just a whole lot of blue. Poor cyan and orange seem pretty under-represented, too.  I hope they do a better job with rainbows.