the images of the cross-shaped hole arrays with differently spaced separations. These arrays were oriented at several different angles, to allow different sampling by the readout pixel array. Figure 6 shows some of these images, not corrected for centroiding systematics, and Fig 7 shows plots from summing pixel rows across one of the cross arms.

The smallest spot separation is 30 microns, centre to centre, so the smallest gap between them is 5 microns. The next smallest gap is 20 microns. The resolution is different for the 3 detectors, as expected from their window gaps and the photon wavelengths (see figs 7 and 8), but in all cases the 20 micron gap is well resolved, and the 5 micron gap is not.

The resolution estimates by both methods agreed well, and table 3 shows the adopted average numbers for the spatial resolution for the 3 detectors. The wavelengths used, and the photocathode gaps are also shown. The ‘predict’ numbers are the values expected from the front-end tube measures. Figure 8 shows these and the dependence of resolution on wavelength and gap, and compares the front-end tube tests before assembly with the final values from the fully integrated detectors. The numbers 