I recently bought a cheap and cheerful hand held spectroscope. Great fun to look at CFL lamps and the modern LEDs. Those LEDs are really good, btw. Also, the 'scope gives a pretty even spread of brightness over the whole visible range. (an equipment check). I have been looking at the spectrum of the setting Sun on a regular basis. I see distinct absorption bands in the yellow / orange region. Blue is a bit attenuated, perhaps and red is continuous again. I would like to know what the bands are due to. I am looking at the Sun, low over the London conurbation and I suspect it could be something to do with that. Any ideas? I must remember to take the scope with me next time I can see a sunset over a clean horizon. Does that justify a short break in Cornwall??