Many astronomers and astrophysicists require large computing resources for their research, which are usually obtained via dedicated (and expensive) parallel machines. Depending on the type of the problem to be solved, an alternative solution can be provided by creating dynamically a computer cluster out of non-dedicated workstations using the Condor High Throughput Computing System and the Master-Worker (MW) framework. As an example of this we show in this paper how a radiative transfer application previously coded with MPI is solved using this solution without the need for dedicated machines.