Blue Sky Spectra

I obtained the spectra of the scattered light from the daytime sky with this arrangement in our west-facing guest bedroom. The cardboard sheet temporarily blocks all the blue sky daylight from the outside, except for a thin slit on the upper portion of the right sheet of cardboard. The camera and CD or DVD is mounted on the tripod and faces away from the slit. Thus the blue skylight passes through the slit, reflects off the CD or DVD, and enters the camera lens. The CD or DVD is held parallel to the front of the camera, about 18 inches away from the camera lens.

The spectrum of scattered skylight on the CD shows blue on the left and red on the right, with some semi-dark absorption lines that are roughly vertical.

The same image of the CD above, but with the absorption lines labeled in the original Fraunhofer letter designations.

Here is the spectrum of the daytime sky light on a DVD, rather than the CD. Notice the spectrum colors are more dispersed (spread out). Notice also the absorption lines are readily apparent on this spectrum too.