Imaging through randomly fluctuating media

The formation of images observed under poor seeing conditions is discussed. Our interest is in situations where the seeing disk (this is the time-averaged image of a small object viewed through a fluctuating medium) is much larger than the true image of the object, so that the seeing problem is severe. We extend a previous discussion of how the theory of interferometry is related to successful solutions to the seeing problem. Two extensions of speckle interferometry, allowing true imaging of arbitary objects, are described. One of them is illustrated by explaining how images of the star Betelgeuse have recently been obtained.