p-mode amplitude spectrum of our best-quality run of 7.9 days, with a duty cycle of 35%, obtained in October 2007 with a SLOAN g filter using two telescopes at different longitudes: the WHT 4.2m in La Palma, equipped with ULTRACAM, and the MDM 1.3m at Kitt Peak. The upper panel shows the spectral window (red), while the other panels from top to bottom show the amplitude spectra of the data and of the residuals after one, two, three, and four prewhitening steps. A plot showing the high quality of the ULTRACAM data is presented in Silvotti et al. (2010).