Speckle imaging with the multi-anode microchannel array detector

This dissertation combines an instrument and a technique that have been studied separately for several years. The instrument is the multi-anode microchannel array (MAMA) detector. This is a photon-counting imaging system which has the ability to record the arrival time of every detected photon and which can distinguish events that arrive only 140 nanoseconds apart. The technique is speckle imaging. In conventional astronomy, fluctuations in the atmosphere above the telescope blur images so that the resolution is typically 1 to 2 arcseconds, much worse than the theoretical diffraction-limited resolution of large telescopes. Speckle imaging allows for reconstruction of image features on a much smaller scale by taking many short exposure images of an object, where over the exposure time the atmospheric fluctuations are effectively frozen. Speckle imaging cameras must therefore have the ability to read out images much faster than most astronomical imaging devices. Since the MAMA detector offers outstanding timing abilities as well as good spatial linearity and is available in a visible light version, it is an excellent choice for the imaging device in a speckle imaging system.; A new MAMA-based speckle system has been built at Stanford University and a study of its performance forms a principle part of this work. Under certain conditions, the phenomenon of channel saturation of the MAMA detector can have significant effects on the signal-to-noise ratio of the speckle imaging results. Channel saturation also leads to a systematic error in the determination of the irradiance ratios of interferometric binary stars. A correction algorithm is described which leads to better estimates of these ratios in simulated data. Four methods of computing correlation functions necessary for producing high-resolution reconstructed images are compared using MAMA speckle data; two of these explicitly make use of the time-tagging ability of the detector. The highest signal-to-noise ratio in power spectra and bispectra is obtained with a weighted running-window method. Reconstructed images of several objects are presented. The MAMA-based speckle imaging system is shown to determine accurate position angles and separations of sub-arcsecond separation binary stars.