The next step is to image a single point light source ~by switching over to a second slide that has been prepared with
just one pinprick—details of the light sources are discussed in Sec. V!. The image appears to be no different than Fig.
1~d!; there is no difference between the images of a single point light source and two unresolved point light sources.
Having established that, a mask with two 1.3-cm holes is now placed in front of the telescope. The two 1.3-cm