Public Lab DIY Spectrometer

[julianh72]

Has anyone made one of these DIY spectrometers, using a webcam and a DVD-R disc:
http://publiclab.org/wiki/spectrometer

I guess the light gathering power of a webcam might be too low to get much of a spectrum through a telescope from anything but the very brightest targets (like the sun, through a solar filter)?

Anyway, for a total outlay of approximately $0 (I have several old webcams and DVD-R discs that I am prepared to sacrifice in the name of science!), it could be fun even to use for daylight handheld spectral analysis.

[julianh72]

Well, I had to see how it works, so I knocked up a very rough version of the Smartphone Spectrometer http://publiclab.org/wiki/foldable-spec last night - it took about 10 minutes and cost precisely nothing - some cardboard, sticky-tape, and one sacrificial DVD-R disc. (See attached photos.)

And ...


...


It actually works!!!!

The two attached spectra were shot through my smartphone camera, but the spectra are actually much clearer when viewed by eye than these shots suggest. I was having some problems getting alignment and focus through my smartphone camera (the spectrometer was hand-held over the camera), and it wasn't helped by the very shoddy workmanship of the rough "instrument"!

Spectra from incandescent light sources such as a halogen globe are nice uniform rainbows, while a "white" LED shows three clear "sub-rainbows" for each of the RGB components, and an emission source such as a Compact Fluorescent light-bulb shows very clear emission lines.

I probably shouldn't really be surprised that it works, but it was very gratifying nonetheless. :)

My next step will be to make a webcam-based Desktop Spectrometer http://publiclab.org/wiki/dsk - for which I will take my time to get better alignment etc, so that it can be calibrated in the on-line app http://spectralworkbench.org/ . (This one might actually cost me $2 to get a suitable housing to mount it in - I already have a webcam that I will pull apart for the image sensor.) I'm not sure whether it will be able to do any astronomical service, but it's still a great little desktop experiment.

[Merlin66]

Julian,
A great introduction to spectroscopy....cheap as chips!
In Tonkin's "Practical Amateur Spectroscopy", p57, David Randell contributes a whole chapter on CD/DVD "spectroscopes"
When you get "bitten" by spectroscopy and want to move up the food chain towards astronomical spectroscopy you'll find the readily available Star Analyser gratings (100 and 200 l/mm) provide a great introduction and allow you to develop processing skills needed as you more forward.
Onwards and Upwards!