Globular clusters are among the most difficult types of objects to observe with standard photoelectric techniques. Among factors which may contribute to measurement error are the centering of apertures in the oftentimes diffuse cores of clusters, the random distribution of bright stars near the cluster centers, and the determination of an adequate sky correction in fields badly crowded by foreground stars. These problems have been well-discussed by a number of authors (see, e.g., Hanes and Brodie 1984, and the references they cite).