Rayleigh's Owl

Rayleigh's Owl (like Rayleigh's Fish ) is made from glass containing a metal vapour that results in a 'perfect' Rayleigh scatterer. When illuminated in different ways, it can mimic the entire range of twilight colours seen in the sky. The two spectra shown here represent the transmission of light through the whole height of the owl (red line) and the scattered blue light looking sideways close to where the light beam enters the glass (blue line). These represent the setting sun and the blue sky respectively. The spectra also show absorption features due to selenium used to remove the green (iron) tint from high quality glasses.

Note that the rise in the scattering curve shoreward of ~400nm is due to uncorrected straylight in the spectrometer. At the time I made this observation, I did not know how to correct for it. Now I do (April 2015). See the comment from me below.

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