The Head-On Collision of Two Equal Mass Black Holes: Numerical Methods
  The head-on collision of two nonrotating axisymmetric equal mass black holes is treated numerically. We take as initial data the single parameter family of time-symmetric solutions discovered by Misner which consists of two Einstein-Rosen bridges that can be placed arbitrarily distant from one another. A number of problems associated with previous attempts to evolve these data sets have been overcome. In this article, we discuss our choices for coordinate systems, gauges, and the numerical algorithms that we have developed to evolve this system. 
Peter Anninos, David Hobill, Edward Seidel, Larry Smarr and Wai-Mo   Suen