Centroid Noise and Precision Astronomical Photometry

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Centroid noise is a random error, or "noise" component of a photometric measurement that results from placement of the measuring aperture on the object being measured. Centroid noise is not widely known as part of the internal error for a photometric measurement. In this Tech Note, I will examine the effect of centroid noise on stellar photometry. This study uses a series of repeated measurements of the same object to show the effect of centroid noise. The software used was Mira Pro, but the identical algorithms are used in Mira MX. A photometric measurement involves measuring two quantities: