Section 8 – Plates

The spectra of pure metals can be compared against the spectra of stars. In this lightbox one sees two photographic plates taken by the Schmidt telescope. The one on the left shows individual stars (in negative). The one on the right is a similar plate taken when the objective prisms were placed at the opening of the Schmidt tube, turning each spot of starlight into a streak of light. A close look at these streaks reveals tiny gaps in the streak, representing spectral lines — colors absorbed by vaporized metals in the atmospheres of those stars.