(a) Sources used for registration and absolute alignment of the X‐ray images are shown in this 0.5–8 keV image. The gaps between CCDs appear less sharp in this image than in Fig. 1 as the overall background level is very low and the image scaling is logarithmic. The diamonds indicate bright sources present in all four Chandra observations used to register the images. The squares indicate X‐ray sources with reliable optical matches in H00 or radio matches in R00 that were used for absolute alignment of the image. A total of 22 sources were used for absolute alignment of the HDF‐N observation; 14 are in the Caltech area. (b) Positional dispersion of the 22 Chandra sources used for absolute alignment with respect to H00 and R00 coordinates; the ellipse shows the rms dispersion of the offsets.