Image of the fully CLEANed periodogram for 1986 January at each position across the He I λ6678 line profile, with the average spectrum shown below as a positional reference. The main signal (at 1.3 day⁻¹) is seen here as a horizontal bar that transverses most of the line profile. Gaps in this bar are found at positions where the CLEAN algorithm has converged on a 1 cycle day⁻¹ alias of the true frequency.