from the article: "The squares show the FOV of each of the 21 CCD modules. Each is 5 sq deg. Note that the gaps between the CCD modules are aligned so that about half of the 15 stars in the FOV brighter than mv=6 fall in these gaps."
We can found no scientific discipline, nor a healthy profession on the technical mistakes of the Department of Defense and IBM. -- Edsger Dijkstra