times when Saturn's satellite Phoebe is within the
         FOV of the Cassini narrow angle camera (CASSINI_ISS_NAC). To
         simplify the problem, restrict the search to a short time
         period where continuous Cassini bus attitude data are
         available.

         Use a step size of 10 seconds to reduce chances of missing
         short visibility events.


      Here we search the same confinement window for times when a
      selected background star is visible. We use the FOV of the
     