We describe a centroiding image photon counting detector intended for photon counting applications in both ground-based and space astronomy. The detector uses a 40 mm diameter proximity focussed microchannel place intensifier and a rapid-scanned CCD readout system with a transputer based electronic processing system for the on-line data processing. An interesting result has been that this system resolves the pore structure in the front microchannel plate of the intensifier, showing that the system can work to the maximum possible resolution using the MCP intensifiers.