The CCD15-30 are able to be close butted, with a dead region of less than 300 microns wide on three sides; to minimise the dead space, adjacent CCDs can be stepped by about 1 mm to overlap by 300 microns.  The imaging area is ~2.5 x 2.5 cm, so that a mosaic of seven would cover the focal plane of 62 mm in diameter, equivalent to 28.4 arcmin. The imaging section has 600 x 600, 40 micron square, pixels; one pixel covers 1.1 x 1.1 arcsec on the FOV; 15 pixels cover the mirror PSF half energy width of 15 arcsec. The readout register is split into two sections, ending in a readout node. The full CCD image can be read out using either node, or read out using both nodes simultaneously, to halve the readout time.