Amplitudes of the first two principal components shown as a function of time (left) or hours from midnight (right). The top row of plots shows the amplitudes for the first principal component, while the bottom row shows the amplitudes for the second principal component. Lines show the result of a linear interpolation. In the top-right plot, the temperature of the optical bench is also plotted, in orange. In the right plots, the principal-component amplitudes for each night are artificially offset by the median amplitude per night. All days are therefore roughly on the same scale, but the y-axis is different from that on the left plots. In the right column, points are colored by the MJD of each exposure.