  In coherent X-ray diffraction microscopy the diffraction pattern generated by
a sample illuminated with coherent x-rays is recorded, and a computer algorithm
recovers the unmeasured phases to synthesize an image. By avoiding the use of a
lens the resolution is limited, in principle, only by the largest scattering
angles recorded. However, the imaging task is shifted from the experiment to
the computer, and the algorithm's ability to recover meaningful images in the
presence of noise and limited prior knowledge may produce aberrations in the
reconstructed image. We analyze the low order aberrations produced by our phase
retrieval algorithms. We present two methods to improve the accuracy and
stability of reconstructions.
