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This paper describes an instrumental artifact which has been observed in three Nicolet P3F diffractometers. In cases where the peaks are very sharp in ω, the artifact causes azimuthal or ψ scans to appear very noisy and to show a complex periodic variation of intensity with ψ. These intensity variations are reproducible. A simple correction is described which, when applied to the data, dramatically improves the appearance of these aberrant ψ scans. This correction is not limited to ψ scans and should improve the quality of all data collected on the machine.