Precision registration (alignment) of images is utilized in dim target detection, temporal change detection, and other surveillance applications. The Cramer-Rao bound on the accuracy of parameter estimation governs the fundamental limit on the accuracy of image registration. This presentation derives the Cramer-Rao bound on registration accuracy, with emphasis on how registration accuracy depends on sensor noise, scene geometry, image characteristics and the number of pixels used in the registration process, and compares the Cramer-Rao bound prediction to registration results from the SAIC IR processing code, STAS, for both synthetically generated scenes and real IR data.