An Optical Corrector Design That Allows a Fixed Telescope to Access a   Large Region of the Sky
  We discuss a family of two-mirror correctors that can greatly extend the field accessible to a fixed telescope such as a liquid mirror telescope. The performance of the corrector is remarkable since it gives excellent images in patches contained within a field greater than 45 degrees. We argue that this performance makes fixed telescopes competitive with tiltable ones. 
E.F. Borra, G. Moretto, and M. Wang