An intensified event-detecting television system for astronomical speckle interferometry

A four-stage electrostatic image intensifier transfer lens coupled to a plumbicon television camera is used both as a photoelectron event-detecting system and as an analogue detector for the Steward speckle camera. The system is capable of continuous logging of photoelectron event data allowing 100 percent utilization of telescope aperture time by use of a Grinnell GMR-27 video digitizer and graphic television display with a special modification for lag-free event detection. Data can be processed on-line at the site or recorded for off-line processing using a standard analogue video recorder. A seeing-corrected reconstruction of the diffraction limited image derived from the speckle interferometric image autocorrelation computed from 200 television frames of the magnified image of a seventh magnitude close visual binary star observed with the Steward 2.3 meter telescope is reported. The system has been applied to speckle interferometry of objects as faint as visual magnitude 16.